Transition to requirejs

Still a work in progress
Upgrade CodeMirrror to 3.1
Remove unused files.
Finish porting main admin functionality to backbone.
Remove unused specs.
Remove all twitter/tweets functionality.

Gotta focus; even though this is a good idea I don't have time for it.
Update gems.
Fix deprecation warning.
Upgade jquery jquery-ui mustache tablesorter.
Re-organize manage buttons.
Add back in facebox support since manage page still uses it.
Reimplement Theme gallery/switching
Update wording and docs
Clean pinky.
Merge branch 'require-js'