Release 2.6.0 Support TCS3400 colour sensor

Adds support for TCS3400 colour sensors found in some "v2" Sense Hats.

Release v2.5.0 - Readthedocs documentation

Added support for readthedocs, in preparation for amalgamating documentation in future.

Release v2.5.1 - Reduce logging level of colour sensor check output

Merge pull request #128 from astro-pi/bugfix/change-logging-to-debug

Change logging level of warning

Release v2.4.0 - RGB property

Adds an RGB property to the colour sensor to make it easier to reuse values.

Release v2.3.1

Adds support for the new TCS34725 colour sensor using smbus.

Release v2.2.0

Now with Sense Stick API implemented