Added the underscore node_module.

node_modules/underscore/cjs/difference.js

@@ -0,0 +1,15 @@
+var restArguments = require('./restArguments.js');
+var _flatten = require('./_flatten.js');
+var filter = require('./filter.js');
+var contains = require('./contains.js');
+
+// Take the difference between one array and a number of other arrays.
+// Only the elements present in just the first array will remain.
+var difference = restArguments(function(array, rest) {
+  rest = _flatten(rest, true, true);
+  return filter(array, function(value){
+    return !contains(rest, value);
+  });
+});
+
+module.exports = difference;