Initial Implementation of new Markdown WYSIWYM editor

Work on #1 

* Swaps out Markdown editor from MarkItUp to markedit
* Implemented for front end and admin views
* Migration to remove deprecated MarkItUp fields

There are some outstanding items that I'd like to address in separate tickets. I've been spending most of my time on this branch as of late rebasing against develop due to other changes. Getting the bulk of the editor swap into develop would allow for less branch management overheard for these related issues.

* Preview pane was proposed to be side by side. Out of the box we have ```above``` and ```below``` support.
* CSS tweaks to align toolbar with bootstrapped textareas
* Admin CSS tweaks to live preview (default admin CSS bleeds into the markdown preview)
* Bring back h1-h6 support? Markedit has a single heading tool, whereas MarkItUp supported h1 (#) through h6~ish