Better url rewriting for compression of CSS files

Proposed solution allows:
* Multiple url rewrites per line (useful when aggregating already minified CSS files)
* Adds https as a valid case not to rewrite
Merge pull request #62 from rakesh-beedasy/master

Allow snake case for set, prepend and append
Merge pull request #61 from rakesh-beedasy/patch-1

Better url rewriting for compression of CSS files
config url
fix asset config
fixing asset config
Merge remote-tracking branch 'upstream/master'