Added code for additional color difference formulae
Removed accidental leftover .swp file from vim.
Adopted the dispatch model for color differences recommended by
@StefanKarpinski
Hard-coded constants and updated commenting in the DIN99* conversion
functions.
Updated constants with additional precision.
Merge pull request #28 from glenn-sweeney/color_diff

Added code for additional color difference formulae
Merge pull request #30 from glenn-sweeney/conversion_cleanup

Hard-coded constants and updated commenting in DIN99*