Updating the footer for edx.org and open edx.

Making the footer look more like the front page.

* Updated SASS for footer
* Updated HTML for open edx and edx.org templates
* Updated stubbed views
* Added !important SASS to overwrite some blanket LMS styles

Updating steve.m.sandbox.edx.org to have the latest changes.
@wedaly @andywaldrop @dianakhuang @griffresch 

@sarina  
Since this is the edX.org footer I'm unclear what the exact approach should be. I can create a number of new settings such as:
PLATFORM_TWITTER_URL = "https://twitter.com/edXOnline"
PLATFORM_MEETUP_URL = "http://www.meetup.com/edX-Global-Community/"
PLATFORM_LINKEDIN_URL = "http://www.linkedin.com/company/edx"
PLATFORM_GOOGLE_PLUS_URL = "https://plus.google.com/+edXOnline/"

and add them to the template, but if I make them generic, such as "http://www.linkedin.com/your/company" then the sandboxes will have broken links out of the box. Any suggestions?