Add "zenodo" DOI badge.
Merge branch 'hotfix/v0.3.2' into develop
Change "colour.colorimetry.lightness_1976" definition signature.
Update "colour.colorimetry.lightness" module references.
Implement "IPT" colourspace.

Closes #114.
Update docstrings and inner variable names in "colour.temperature.cct" module.
Fixed docstrings.

Aligned first line of reference to next tab.
Instead of repeating the main reference in each function, it is now cited using standard reST citations
Fixed typo in function signature IPT_TO_XYZ -> IPT_to_XYZ
Added module methods to sub-package __init__.py file
Implements unit tests for colour.models.ipt module
Merge pull request #115 from colour-science/feature/ipt

PR: Implement support for "IPT" colourspace.
Update docstrings and inner variable names in "colour.colorimetry.lightness" module.
Update various docstrings in "colour.colorimetry.luminance" module and change "colour.colorimetry.luminance_1976" definition signature.
Code formatting.
Update various docstrings in "colour.colorimetry.lightness" module.
Update ".gitignore" file.
Update "Numpy" version in "setup.py" file.
Add missing documentation building dependencies to "setup.py" file.
Add disappeared "CIE Illuminant D Series" "D60" chromaticity coordinates for "CIE 1964 10 Degree Standard Observer".

Reference #27.
Remove unneeded commented code.