Bug 976227 - dashboard template

Rough template, more polish on the way.
Updated tests for landing->home.
No, really, deploys don't need user input.
Base template and home page updates
Add contributing guidelines document.
Bug 976794: Add model for news items and display them on dashboard.
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.
Store the type of banner that links were created by.
Bug 976782: Calculate and display milestones.
Tests!