Adafruit-circuitpython-rtttl

- 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-rtttl`.

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

Thanks to jedgarpark for adding another example to the README.

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/rtttl/en/latest/) for info on how to use it.

* Fixed the library so multiple calls to `play` work as expected and don't get a "Pin in use" exception.

Documentation is available [on ReadTheDocs](https://circuitpython.readthedocs.io/projects/rtttl/en/latest/).

To use, simply load the [Adafruit CircuitPython Library Bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle/releases) or download the corresponding file from this release.

Thanks to tannewt for the great work!

To use, simply load the [Adafruit CircuitPython Library Bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle/releases) or download the correct file from this release.

Thanks to brentru for the great work!

Example playing two songs