Pyld

Fixed
- Use `__about__.py` to hold versioning and other meta data. Load file in
`setup.py` and `jsonld.py`. Fixes testing and installation issues.

- See git history for changes.

[jsonld.js]: https://github.com/digitalbazaar/jsonld.js
[Requests]: http://docs.python-requests.org/
[aiohttp]: https://docs.aiohttp.org/