Add branch-alias

This way people can require "0.3.*" and get stable vs unstable
versions depending on their minimum-stability, without having to
deal with the pains of dev-master.
Merge pull request #368 from igorw/patch-1

Add branch-alias
Add support for media query variables #335
add test for variable in media
add unit function, fixes #367
support nested interpolations #345
support interpolation inside of selectors fixes #370 #372 #369 #356
performance boost for selector parsing with interpolations
Merge remote-tracking branch 'upstream/master'