Bump to v4.4.0.

difference.js

@@ -21,7 +21,7 @@ var baseDifference = require('./_baseDifference'),
  */
 var difference = rest(function(array, values) {
   return isArrayLikeObject(array)
-    ? baseDifference(array, baseFlatten(values, false, true))
+    ? baseDifference(array, baseFlatten(values, 1, true))
     : [];
 });