Add "Travis-CI" notifications to "Slack".
Implement "Smits (1999)" reflectance recovery method skeleton.
Implement support for "Smits (1999)" reflectance recovery method.

Closes #144.
Add notebook link to "colour.recovery.smits1999" module.
Rename "colour.RGB_to_spd_smits1999" definition to "colour.RGB_to_spectral_smits1999".
Update bibliography.
Merge pull request #145 from colour-science/feature/recovery

PR: Implement support for "Smits (1999)" reflectance recovery method.