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diff --git a/node_modules/underscore.string/levenshtein.js b/node_modules/underscore.string/levenshtein.js
new file mode 100644
index 000000000..85f220c1f
--- /dev/null
+++ b/node_modules/underscore.string/levenshtein.js
@@ -0,0 +1,52 @@
+var makeString = require('./helper/makeString');
+
+/**
+ * Based on the implementation here: https://github.com/hiddentao/fast-levenshtein
+ */
+module.exports = function levenshtein(str1, str2) {
+  'use strict';
+  str1 = makeString(str1);
+  str2 = makeString(str2);
+
+  // Short cut cases  
+  if (str1 === str2) return 0;
+  if (!str1 || !str2) return Math.max(str1.length, str2.length);
+
+  // two rows
+  var prevRow = new Array(str2.length + 1);
+
+  // initialise previous row
+  for (var i = 0; i < prevRow.length; ++i) {
+    prevRow[i] = i;
+  }
+
+  // calculate current row distance from previous row
+  for (i = 0; i < str1.length; ++i) {
+    var nextCol = i + 1;
+
+    for (var j = 0; j < str2.length; ++j) {
+      var curCol = nextCol;
+
+      // substution
+      nextCol = prevRow[j] + ( (str1.charAt(i) === str2.charAt(j)) ? 0 : 1 );
+      // insertion
+      var tmp = curCol + 1;
+      if (nextCol > tmp) {
+        nextCol = tmp;
+      }
+      // deletion
+      tmp = prevRow[j + 1] + 1;
+      if (nextCol > tmp) {
+        nextCol = tmp;
+      }
+
+      // copy current col value into previous (in preparation for next iteration)
+      prevRow[j] = curCol;
+    }
+
+    // copy last col value into previous (in preparation for next iteration)
+    prevRow[j] = nextCol;
+  }
+
+  return nextCol;
+};