Add tests for new models and banner creation process.

Also fixes issues with existing tests:
- Jenkins runs Python 2.6, which doesn't support using assert_raises as
  a context manager, so we use Django's version on TestCase, which uses
  the version from unittest2, which does support it.
- Set BannerFactory to be an abstract factory.
Add link referral view that sends data to GA and use it for banner code.
Add management command for retrieving referral data and fix model.
Tests!
Add google-api-python-client.
Add setting for stylus support.
Base template, stubbed out home page
Bug 976231 - leaderboard template

With a few base changes, too
Merged before Craig could fix the capitalization, doh!
Add helper for retrieving gravatars.
Bug 976809: Add management command for updating leaderboard.

- Also update collect_ga_data to batch bulk data insertion in case MySQL
  decides it's not waiting for a crapton of data.
- Add a script to bin for running the nightly update tasks.
Partial integration of leaderboard template.