Fixes #1 bourbon border-radius mixin deprecation

Signed-off-by: Tommaso Visconti <tommaso.visconti@gmail.com>
Merge pull request #2 from tommyblue/border-radius-fix

Fixes #1 bourbon border-radius mixin deprecation
Preview size is now an array of dimensions
Fix
ImageMagick shouldn't consider pdf as images
Don't use image? for file type check
Add github pointer for gem in README
Merge pull request #3 from nbrew/github-in-readme

Add github pointer for gem in README
Trying to prevent blow ups on DataNotFound in preview
Merged latest from the source repo
Bad merge mojo