Added brightness parameter as fix to error in test.py and the module test function

[robgithub]

Found python/examples/test.py had fatal error when run
Traceback (most recent call last): File "test.py", line 41, in <module> r, g, b = [int(c * 0.99) for c in mote.get_pixel(channel + 1, pixel)] ValueError: too many values to unpack
This was duplicated in the python/library/mote/init.py module file

Found that get_pixel was returning RGB+Brightness, so fix was to accept a brightness parameter.

Also updated the documentation python/documentation/Function-reference.md to reference this.

[Gadgetoid]

Good spot! Thank you for raising a PR.