Fixing error in documentation snippet
First draft of Tiff saving
Can save many pixel types in Tiff
Cleaning up debug statement for Tiff file writing
Updated documentation for Tiff saving
Detecting and rejecting Progressive Jpeg (to be better handled after)
Bumping the JuicyPixel version to 3.1.1
Introducing a mixWith pixel method, to help implement generic blending/pixel addition function.