Ensures all uppercase urls are turned into lowercase.
Ensures all uppercase urls are turned into lowercase.

Ommited by mistake in 80418fac5bf7ce6bfe98f75dcb4c6c3aeb185d0d.

MartyIX/clean-css,yomed/clean-css,shelsonjava/clean-css,scottgonzalez/clean-css,GerHobbelt/clean-css,island205/clean-css,stuht/clean-css,jakubpawlowicz/clean-css,vlajos/clean-css