fix: pkg: update license number in ``README.rst``.

fix: ``rgb2hsl`` would produce invalid hsl triplet when red, blue, gr…

…een component would be all very close to ``1.0``. (fixes #30)

Typically, saturation would shoot out of range 0.0..1.0. That could then
lead to exceptions being casts afterwards when trying to reconvert this
HSL triplet to RGB values.

new: pkg: added windows tests thanks to ``appveyor``.

fix: doc: spellcheck and typo cleanup (fixes #19) !minor

fix: pkg: ``colour`` not importable after installation. (fixed #15)

This was a consequence of a missing ``module`` declaration in
``setup.cfg``. The fact that the lengthy travis tests didn't catch that
one earlier showed that they were flawed. These were corrected also.

new: provide all missing *2* function by combination with other exist…

…ing ones (fixes #13).

fix: pkg: avoid looping in ``setup.py`` in case ``./autogen.sh`` fails.

new: added ``make_color_factory`` to customize some common color attr…

…ibutes.

new: colour is now compatible with python3.

fix: pkg: missing ~/.gitchangelog.rc and added some docs on how to in…

…stall ``colour`` from git and from pip.