Mentioning that blending operations are applied to each channel independently.
Fixes #45
Clarifying the need for a filename extension or an extension in the options.
Fixes #28.
Merge pull request #83 from ybakos/45_blendMode

Mentioning that blending operations are applied to each channel independently
Merge pull request #84 from ybakos/28_loadTable

Clarifying the need for a filename extension or an extension in the options