Accept dashes and numbers in http urls.

Add some tests for http urls with dashes and numbers in them.
Accept data urls as valid urls.

Add tests for data urls.
Fix broken test by removing incorrectly identified duplicate.
Updates CHANGELOG with url bug fixes

This is a modified pull request from
https://github.com/zmoazeni/csscss/pull/31 that squashes some code/test
commits. Thanks @carsonmcdonald for the hand.