Refs #269: Make page footer fixed

We want the page footer to be pushed down to the bottom on short
pages, and appear normally after the content on longer pages.

Had to rearrange the html a bit to get this all working with
bootstrap and responsive.

Branch: feature/269-footer-at-bottom
Refs #269: Merge remote-tracking branch 'remotes/origin/release-0.12.0' into feature/269-footer-at-bottom

Conflicts:
	rapidsms/templates/layout.html

Branch: feature/269-footer-at-bottom
Refs #269: Bump copyright in page footer to 2013
Branch: feature/269-footer-at-bottom
Merge remote-tracking branch 'remotes/origin/feature/269-footer-at-bottom' into feature/268-remove-rapidsms-tabs

Branch: feature/268-remove-rapidsms-tabs
Refs #268: Remove RAPIDSMS_TABS

Get rid of RAPIDSMS_TABS setting and the template tag that used it.

Instead include the template "rapidsms/_nav_bar.html" at that point
in layout.html, provide a sample file with commented example links.

Branch: feature/268-remove-rapidsms-tabs
Merge remote-tracking branch 'remotes/origin/release-0.12.0' into feature/268-remove-rapidsms-tabs

Conflicts:
	rapidsms/templates/layout.html

Branch: feature/268-remove-rapidsms-tabs
Remove RAPIDSMS_TABS from tests/default.py
Branch: feature/268-remove-rapidsms-tabs
Start a doc page on how the frontend works. Document how to control the links at the top of each page.
Branch: feature/268-remove-rapidsms-tabs
Add a bit of padding above the footer, and a few comments
Branch: feature/268-remove-rapidsms-tabs
Merge pull request #268 from rapidsms/feature/268-remove-rapidsms-tabs

Remove RAPIDSMS_TABS