Precompile less files.
Move img folder to images
Fix useminPrepare task to rewrite relative css urls.

First, tell useminPrepare to only 'cssmin' our css files (dropping the
concat task). See https://github.com/yeoman/grunt-usemin/issues/225.

Second, tell cssmin to rewrite relative urls to be relative to our app
directory.
Use absolute paths

Since we're compiling our less before cssmin runs, cssmin will try to
rewrite urls relative to the .tmp directory less outputs to. This stops
that.
Merge pull request #34 from cloudspace/64399706_assets

Fix Assets on Deploy