bug 1079932 - Add docs for data repository

Data is stored at https://github.com/jwhitlock/browsercompat-data.  Can
be moved to Mozilla-owned repo, or a new repo can be created using
tools/download_data.py.  Data and API code is at
http://browsercompat.herokuapp.com.
bug 1079932 - Improve browse app for Versions

- Display dates as 2014-12-05 w/o hour / minute / second
- Wrap release_notes_uri links in <a></a>
fix bug 1079932 - More ordering in JSON API

- Translated fields - 'en' first, then other languages in alpha order
- Use OrderedDict more to preserve order
- Use unicode more consistantly
- Use JSON serializer in diffs, to preserve field order
- When order doesn't matter, sort related IDs by ID in cache