Adafruit-circuitpython-mcp4725

- 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-mcp4725`.

Read the [docs](http://circuitpython.readthedocs.io/projects/mcp4725/en/latest/) for info on how to use it.

Thanks to sommersoft for the documentation refinement.

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](http://circuitpython.readthedocs.io/projects/mcp4725/en/latest/) for info on how to use it.

Initial release to trigger Travis MPY generation.