Merge pull request #25 from joakimbeng/master

Adding the ability to use variables in media queries and such
bin: added column props (fixes #26)
Merge pull request #27 from guille/add/column-family-prefix

bin: added column props (fixes #26)
add prefix example to media
add prefix visiting for @media
Merge branch 'master' of github.com:visionmedia/rework
add media prefix test case
Release 0.12.2