Initial working commit of native OS X tiff reader
Fix filename handling
Fixes malloc error on second imread() call
Better metadata handling and now handles 8 & 16 bit tiffs
Loads images lacking tiff `imagedescription`, like .pngs
Clean handling of single frame images
Only pull tiff description dictionary from tiffs
Add default image description

Avoids errors if not set by the time the image properties dict is constructed
Add some basic tests
Add rudimentary support for RGB images
Adjust image array size and properties
Ruthlessly swipe Tim's approach with ImageMagick
Set up platform-dependent tests
Check if file is not an image
Document changes, and provide instructions for disabling
Merge branch 'rsr/osx_io'