Merge pull request #75 from nwin/master

Add benchmark
Merge pull request #76 from nwin/master

Extended image::IoError to hold io::IoError.
Merge pull request #77 from nwin/master

Provide better error messages for unsupported features.
Transmute the vector with the pixel instead of copying it. Fixes #78
Merge pull request #80 from nwin/master

Better tests
Wording + use type inference.
Corrected typo
typo…
Merge pull request #81 from nwin/transmute_image_buf

Transmute the vector with the pixels instead of copying it.
Removed duplicate assertion. This is identical to the first match arm. This assertion is repeated also in the n arm.