Streaming-form-data

- Performance: avoid repeated function calls to check the buffer length

- Add Sphinx documentation and make them available on
https://streaming-form-data.readthedocs.org

- Provide `parser.register` function for handling uploaded parts,
replacing the `expected_parts` argument
- Remove `Part` class from the user-facing API since it just makes the
API look messy and verbose
- Update documentation

- Include upload form in tornado usage example
- Call `unset_active_part` when a delimiter string is found

- Update README and tornado usage example
- Adjust import paths for the `Part` class

- Initial release

[NteRySin]: https://github.com/NteRySin
[Wouterkoorn]: https://github.com/Wouterkoorn
[gabrielcedran]: https://github.com/gabrielcedran
[hbusul]: https://github.com/hbusul
[ibrewster]: https://github.com/ibrewster
[jasopolis]: https://github.com/jasopolis
[kolomenkin]: https://github.com/kolomenkin
[mephi42]: https://github.com/mephi42
[raethlein]: https://github.com/raethlein
[remram44]: https://github.com/remram44
[tokicnikolaus]: https://github.com/tokicnikolaus