Fix handling of non-uint8 imags for PIL imsave.
Update build requirements and documentation
Reorganized dependencies in DEPENDS.txt.
Fix install_requires string formatting
Use img_as_ubyte instead of the previous hack
Add to the docstring notes.
Add to docstring notes
Fix errant changes
Add support for tif floating point and 16bit files
Handle case where format_str is None
Add note about 2D TIFF file support
Add handling for uint16 and integer types.