Likes: Fixes issues where likes don't load.

- Moved the scripts to the bottom and the style to the top.
- Makes sure that the likes work as expected by making sure that the
master iframe is loaded after scripts are loaded.
props @zinigor for contributions to this PR.
Merge pull request #1331 from Automattic/likes/fix-script-queue

Likes: Moved the call to enqueue_scripts into the action body making sure that scripts get loaded and that the master iframe is created after the scripts get added to the page.  props @zinigor