Feature/tinymce

First stab at more robust implementation of the "module" button in the editor. Added a third option (to go along with already-existent "pull quote" and "aside" options) called "embedded media," and added a new width option that tries to extract the width (and height!) from the iframe (or whatever's being embedded).

I think it works pretty well — at least as well as it did for the asides and pull quotes, anyway. :)