Adafruit-circuitpython-hid

- Added `setup.py`
- Added PyPI release info to `.travis.yml`
- Updated `requirements.txt`
- Added a more comprehensive `.gitignore`

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-hid`.

Read the [docs](http://circuitpython.readthedocs.io/projects/hid/en/latest/) for info on how to use it.

Consumer control and gamepad documentation was missing from `api.rst`.

To use in CircuitPython, download the .mpy file and copy it to the `lib` folder on the `CIRCUITPY` drive. Or, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

Read the [docs](https://circuitpython.readthedocs.io/projects/hid/en/latest/) for info on how to use it.

ConsumerControl was not passing 16-bit codes properly. Thanks zeevro!

For use with gamepad support in CircuitPython 3.0.0-alpha.6.