Fix issue with hyphens in file validation mime types

Addresses victorjonsson#646, which reported that mime types in file validations were
being parsed incorrectly when they contained hyphens. This change
ensures that we only split the allowed file types string at commas and
trailing white space and not at hyphens.

Author: Nick Holden

src/modules/file.js

@@ -25,7 +25,7 @@
       * @return {Array}
       */
       _getTypes = function($input) {
-        var allowedTypes = $.split( ($input.valAttr('allowing') || '').toLowerCase() );
+        var allowedTypes = ($input.valAttr('allowing') || '').toLowerCase().split(/,\s*/);
         if ($.inArray('jpg', allowedTypes) > -1 && $.inArray('jpeg', allowedTypes) === -1) {
           allowedTypes.push('jpeg');
         }