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diff --git a/vendor/zendframework/zend-stdlib/src/PriorityQueue.php b/vendor/zendframework/zend-stdlib/src/PriorityQueue.php
new file mode 100644
index 000000000..2a1628731
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+++ b/vendor/zendframework/zend-stdlib/src/PriorityQueue.php
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+<?php
+/**
+ * Zend Framework (http://framework.zend.com/)
+ *
+ * @link      http://github.com/zendframework/zf2 for the canonical source repository
+ * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   http://framework.zend.com/license/new-bsd New BSD License
+ */
+
+namespace Zend\Stdlib;
+
+use Countable;
+use IteratorAggregate;
+use Serializable;
+
+/**
+ * Re-usable, serializable priority queue implementation
+ *
+ * SplPriorityQueue acts as a heap; on iteration, each item is removed from the
+ * queue. If you wish to re-use such a queue, you need to clone it first. This
+ * makes for some interesting issues if you wish to delete items from the queue,
+ * or, as already stated, iterate over it multiple times.
+ *
+ * This class aggregates items for the queue itself, but also composes an
+ * "inner" iterator in the form of an SplPriorityQueue object for performing
+ * the actual iteration.
+ */
+class PriorityQueue implements Countable, IteratorAggregate, Serializable
+{
+    const EXTR_DATA     = 0x00000001;
+    const EXTR_PRIORITY = 0x00000002;
+    const EXTR_BOTH     = 0x00000003;
+
+    /**
+     * Inner queue class to use for iteration
+     * @var string
+     */
+    protected $queueClass = 'Zend\Stdlib\SplPriorityQueue';
+
+    /**
+     * Actual items aggregated in the priority queue. Each item is an array
+     * with keys "data" and "priority".
+     * @var array
+     */
+    protected $items      = [];
+
+    /**
+     * Inner queue object
+     * @var SplPriorityQueue
+     */
+    protected $queue;
+
+    /**
+     * Insert an item into the queue
+     *
+     * Priority defaults to 1 (low priority) if none provided.
+     *
+     * @param  mixed $data
+     * @param  int $priority
+     * @return PriorityQueue
+     */
+    public function insert($data, $priority = 1)
+    {
+        $priority = (int) $priority;
+        $this->items[] = [
+            'data'     => $data,
+            'priority' => $priority,
+        ];
+        $this->getQueue()->insert($data, $priority);
+        return $this;
+    }
+
+    /**
+     * Remove an item from the queue
+     *
+     * This is different than {@link extract()}; its purpose is to dequeue an
+     * item.
+     *
+     * This operation is potentially expensive, as it requires
+     * re-initialization and re-population of the inner queue.
+     *
+     * Note: this removes the first item matching the provided item found. If
+     * the same item has been added multiple times, it will not remove other
+     * instances.
+     *
+     * @param  mixed $datum
+     * @return bool False if the item was not found, true otherwise.
+     */
+    public function remove($datum)
+    {
+        $found = false;
+        foreach ($this->items as $key => $item) {
+            if ($item['data'] === $datum) {
+                $found = true;
+                break;
+            }
+        }
+        if ($found) {
+            unset($this->items[$key]);
+            $this->queue = null;
+
+            if (! $this->isEmpty()) {
+                $queue = $this->getQueue();
+                foreach ($this->items as $item) {
+                    $queue->insert($item['data'], $item['priority']);
+                }
+            }
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Is the queue empty?
+     *
+     * @return bool
+     */
+    public function isEmpty()
+    {
+        return (0 === $this->count());
+    }
+
+    /**
+     * How many items are in the queue?
+     *
+     * @return int
+     */
+    public function count()
+    {
+        return count($this->items);
+    }
+
+    /**
+     * Peek at the top node in the queue, based on priority.
+     *
+     * @return mixed
+     */
+    public function top()
+    {
+        return $this->getIterator()->top();
+    }
+
+    /**
+     * Extract a node from the inner queue and sift up
+     *
+     * @return mixed
+     */
+    public function extract()
+    {
+        return $this->getQueue()->extract();
+    }
+
+    /**
+     * Retrieve the inner iterator
+     *
+     * SplPriorityQueue acts as a heap, which typically implies that as items
+     * are iterated, they are also removed. This does not work for situations
+     * where the queue may be iterated multiple times. As such, this class
+     * aggregates the values, and also injects an SplPriorityQueue. This method
+     * retrieves the inner queue object, and clones it for purposes of
+     * iteration.
+     *
+     * @return SplPriorityQueue
+     */
+    public function getIterator()
+    {
+        $queue = $this->getQueue();
+        return clone $queue;
+    }
+
+    /**
+     * Serialize the data structure
+     *
+     * @return string
+     */
+    public function serialize()
+    {
+        return serialize($this->items);
+    }
+
+    /**
+     * Unserialize a string into a PriorityQueue object
+     *
+     * Serialization format is compatible with {@link Zend\Stdlib\SplPriorityQueue}
+     *
+     * @param  string $data
+     * @return void
+     */
+    public function unserialize($data)
+    {
+        foreach (unserialize($data) as $item) {
+            $this->insert($item['data'], $item['priority']);
+        }
+    }
+
+    /**
+     * Serialize to an array
+     *
+     * By default, returns only the item data, and in the order registered (not
+     * sorted). You may provide one of the EXTR_* flags as an argument, allowing
+     * the ability to return priorities or both data and priority.
+     *
+     * @param  int $flag
+     * @return array
+     */
+    public function toArray($flag = self::EXTR_DATA)
+    {
+        switch ($flag) {
+            case self::EXTR_BOTH:
+                return $this->items;
+            case self::EXTR_PRIORITY:
+                return array_map(function ($item) {
+                    return $item['priority'];
+                }, $this->items);
+            case self::EXTR_DATA:
+            default:
+                return array_map(function ($item) {
+                    return $item['data'];
+                }, $this->items);
+        }
+    }
+
+    /**
+     * Specify the internal queue class
+     *
+     * Please see {@link getIterator()} for details on the necessity of an
+     * internal queue class. The class provided should extend SplPriorityQueue.
+     *
+     * @param  string $class
+     * @return PriorityQueue
+     */
+    public function setInternalQueueClass($class)
+    {
+        $this->queueClass = (string) $class;
+        return $this;
+    }
+
+    /**
+     * Does the queue contain the given datum?
+     *
+     * @param  mixed $datum
+     * @return bool
+     */
+    public function contains($datum)
+    {
+        foreach ($this->items as $item) {
+            if ($item['data'] === $datum) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Does the queue have an item with the given priority?
+     *
+     * @param  int $priority
+     * @return bool
+     */
+    public function hasPriority($priority)
+    {
+        foreach ($this->items as $item) {
+            if ($item['priority'] === $priority) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Get the inner priority queue instance
+     *
+     * @throws Exception\DomainException
+     * @return SplPriorityQueue
+     */
+    protected function getQueue()
+    {
+        if (null === $this->queue) {
+            $this->queue = new $this->queueClass();
+            if (! $this->queue instanceof \SplPriorityQueue) {
+                throw new Exception\DomainException(sprintf(
+                    'PriorityQueue expects an internal queue of type SplPriorityQueue; received "%s"',
+                    get_class($this->queue)
+                ));
+            }
+        }
+        return $this->queue;
+    }
+
+    /**
+     * Add support for deep cloning
+     *
+     * @return void
+     */
+    public function __clone()
+    {
+        if (null !== $this->queue) {
+            $this->queue = clone $this->queue;
+        }
+    }
+}