Merge branch 'release/0.4.0'
Merge branch 'release/0.4.1'
Merge branch 'release/0.5.0'
Merge branch 'release/0.5.1'
Update README.md
If config.extensibility is defined and is a string, update build output to reflect the CSS prefix.
Merge branch 'develop' of github.com:doctyper/grunt-modernizr into develop