don't try to read absolute urls
use regex
Allow string interpolation in @extend.
Fixes extends within a loop.
Merge pull request #957 from blakeembrey/extend-interpolation

Allow selector interpolation in @extend
Merge pull request #960 from blakeembrey/extend-loop

Fixes @extend within a loop
Merge pull request #948 from scien/master

Don't Evaluate Absolute URLs
make leading quotes optional for absolute url regexp