Adafruit-circuitpython-amg88xx

- 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-amg88xx`.

Read the [docs](http://circuitpython.readthedocs.io/projects/amg88xx/en/latest/) for info on how to use it.

Thanks to brentru for the great work!

Thanks to brentru-2 for the great work!

Thanks to tannewt for the great work!