decode_bits() no longer modifies its input argument

Updating major version number since this is an API change:
decode_bits was removing header from the input argument and thus modifying it, which could fail it were called multiple times with the same argument.

To use in CircuitPython, simply install the Adafruit CircuitPython bundle.

To use in CPython, pip3 install adafruit-circuitpython-irremote.

Read the docs for info on how to use it.