Adafruit-circuitpython-mpl3115a2

- 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-mpl3115a2`.

Read the [docs](http://circuitpython.readthedocs.io/projects/mpl3115a2/en/latest/) for info on how to use it.

Thanks to siddicious for the fix!

Fixes the release directory in a different way.

Except Travis will not change directories permanently

Initial release for MPY generation.