Added support for variables in certain at-rules (keyframes, namespace, charset).
Merge pull request #1860 from seven-phases-max/variables-in-atrules-2

Support for variables in certain at-rules.
Create travis file
add an npm install because it seems if you add an

install step it doesn't run npm install
Remove 0.6 since it fails
Up the version of node to the required version
Add travis icon
Add travis to readme
Merge remote-tracking branch 'origin/master' into detached-rulesets