Bug 1079932 - Add data

*This commit builds on #16.  Merge that first*

This pull request adds support for downloading and uploading web compat data using the API.  Most of the changes are in the tools/ folder:

- `resources.py` - Hold API data, serialize / deserialize from JSON API, compare collections of resources
- `load_spec_data.py` and `load_webcompat_data.py` - Converted to use resources, and to use sync paradigm rather than loading to an empty API.
- `download_data.py` - Download API data as JSON API to a folder
- `upload_data.py` - Upload API data from a folder

A separate repo contains a starting data set of browser, version, feature, maturity, and specification data:

https://github.com/jwhitlock/browsercompat-data

This data is loading in a fresh API:

http://browsercompat.herokuapp.com

These changes and repos enable a github-based workflow:

1. Fork and branch `browsercompat-data`
2. Import into a local copy of web-platform-compat using `upload_data.py`
3. Make some changes in the local copy
4. Export changes using `download_data.py`
5. Push changes to `browsercompat-data` fork, submit a pull request

Once there is a web-based editing interface, a periodic script or edit hook could ensure `browsercompat-data` is kept in sync with the API.