Replace serialized "+" with space (#521)

* Replace serialized "+" with space

Fixes regression introduced by #262
https://www.drupal.org/node/2860158#comment-12011599

Author: markhalliwell

src/jquery.form.js

@@ -346,6 +346,8 @@
 			var i, part;
 
 			for (i = 0; i < len; i++) {
+				// #252; undo param space replacement
+				serialized[i] = serialized[i].replace(/\+/g, ' ');
 				part = serialized[i].split('=');
 				// #278; use array instead of object storage, favoring array serializations
 				result.push([decodeURIComponent(part[0]), decodeURIComponent(part[1])]);