BUG Trigger TinyMCE onChange more frequently

Periodically check for inline changes when focused,
since TinyMCE's onChange only fires on certain actions
like inserting a new paragraph, as opposed to any user input.
This also works around an issue where the "save" button
wouldn't trigger if the click is the cause of a "blur" event
after an (undetected) inline change. This "blur" causes onChange
to trigger, which will change the button markup to show "alternative" styles,
effectively cancelling the original click event.
Merge pull request #2052 from chillu/pulls/onchange-tinymce-trigger

BUG Trigger TinyMCE onChange more frequently