A Very Useful Little Module For Mixing Colours
==============================================

Suppose you are yadda yadda blah blah blah

    >>> from mylittlemodule import mix_colours

The simplest use case is when you have two colours and an opacity value
between 0 and 1.0

    >>> mix_colours(...)

    >>> [1, 2, 3,
    ...  4, 5, 6]
    [...]

    >>> print '*'; print_anything()
    *
    ...