Fixed an issue where the imports caused devices that only had `pwmio` (and did not have `audioio`) to be mistakenly blocked from importing this library due to requiring `adafruit_waveform`.
To use in CircuitPython, simply install the [Adafruit CircuitPython Bundle](https://circuitpython.org/libraries).
To use in CPython, `pip3 install adafruit-circuitpython-rtttl`.
Read the [docs](http://circuitpython.readthedocs.io/projects/rtttl/en/latest/) for info on how to use it.