Fix create-dev-env script for Mac OS 10.8 and latest stable rvm

Add support for video download link

Now when you hit the TAB key in codemirror, it will insert 4 spaces.

Firefox bug fix

Add styling for code grader responses

Make collapsibles not collapse the entire page

- need to set text of the link, not the document
- there was something funny with the operator precedence in the ternary operator (was getting 'true', instead of a string)

Kimth/js refactor

fix a bug: can_load() should check for the 'load' permission.

- triggered by anon users when all courses have started (or start dates are off).

Feature/victor/status banner

Add a download link to the video player. The link is defined in the
content xml using the following structure:

<video youtube="youtubestring">
  <source src="video_link"/>
</video>

Don't ignore .py files in static files dirs

- still needs style
- will cache for 10 seconds

Feature/cdodge/cms permissions management

add distinct 'admin' role separate from 'editors'. Only 'admins' should be able to add/remove editors.

fixed custom tab box-sizing glitch in firefox

Renamed jsloader to match up with the content more explicitly; refactored Collapsible out into its own library

make codemirror use visible tabs

added moderator label styles

Fix to update the max_grade cache on StudentModule