White space
Update to use standard srcset syntax.

http://ericportis.com/posts/2014/srcset-sizes/
http://scottjehl.github.io/picturefill/
http://picture.responsiveimages.org/
Fix failing test

Ensure we send in correct type of data in specs.
And handle undefined values in paths.
Switch repo for dep

So we can install npm modules again.

Previous repo is not available anymore.