Bump to v4.2.1.

lodash.union/index.js

@@ -1,5 +1,5 @@
 /**
- * lodash 4.2.0 (Custom Build) <https://lodash.com/>
+ * lodash 4.2.1 (Custom Build) <https://lodash.com/>
  * Build: `lodash modularize exports="npm" -o ./`
  * Copyright 2012-2016 The Dojo Foundation <http://dojofoundation.org/>
  * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
@@ -17,6 +17,7 @@ var baseFlatten = require('lodash._baseflatten'),
  *
  * @static
  * @memberOf _
+ * @since 0.1.0
  * @category Array
  * @param {...Array} [arrays] The arrays to inspect.
  * @returns {Array} Returns the new array of combined values.