Merge branch 'hotfix/v0.3.2'
Update docstrings in "colour.colour.models.rgb_colourspace" module.
Cleanup imports in "colour.colorimetry.dataset.cmfs" module.
Update docstrings in "color.models.cie_luv" module.
Ensure some figures settings can be overridden.
Rename "to_RGB" and "to_XYZ" parameters and methods to respectively "XYZ_to_RGB_matrix" and "RGB_to_XYZ_matrix".
Move the "Hex Triplet" code to its own dedicated module in the "notation" sub-package.

Closes #117.
Fix issue with "colour.SpectralShape.range" method returning an extra number in some conditions.

Closes #140.
Update  "colour.SpectralShape.range" method with stronger implementation.

Closes #140.
Add "Travis-CI" notifications to "Slack".
Implement "Smits (1999)" reflectance recovery method skeleton.
Ensure "RGB" conversion objects accept any kind of "array_like" input.
Add remaining relevant "Pointer's Gamut" data.

Closes #21.
Update "Pointer's Gamut" related figures.
Add "Travis-CI" notifications to "Slack".
Implement "__pow__" magic method for "colour.SpectralPowerDistribution" class.
Implement "__pow__" magic method for "colour.TriSpectralPowerDistribution" class.
Fix doctests for "colour.SpectralPowerDistribution" and "colour.TriSpectralPowerDistribution" classes.
Ensure proper "colour.SpectralPowerDistribution.__pow__" and "colour.TriSpectralPowerDistribution.__pow__" methods doctests ellipsis.
Add various new light sources.

Closes #141.