Expand 1, 2, 4 bit grayscale images to Grey(8)
Reading of paletted images.
Scale < 8 bit images to full 8 bit.
Added clarifying comment.
Merge pull request #72 from nwin/master

Switch to new byte string syntax for chunk name matching.
Add ImageBuf::into_vec
Merge pull request #73 from cmr/master

Add ImageBuf::into_vec
Update Travis CI
Merge pull request #71 from nwin/support_nbpp

Support pngs with < 8 bit per pixel
Remove path setting
Merge branch 'pr/74'