Modified the colormap to read as an vector of byte triplets. Also
removed option value on Photometric Interpetation and added test for the
colormap reading.
Merge branch 'master' of git://github.com/geotrellis/geotrellis into feature/geotiff-reader-colormap-array
Merge pull request #854 from johanstenberg92/feature/geotiff-reader-colormap-array

Added extended parsing of the colormap data.