Remove unused import

Author: nox

src/color.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use std::ascii::AsciiExt;
 use std::fmt;
 
 use super::{Token, Parser, ToCss};