Use the new thread-locals.

cf. https://github.com/rust-lang/rust/commit/bad1062caaaefe0963d7b8513786c8283e74f1e7
Merge pull request #4 from ArtemGr/patch-1

Use the new thread-locals.
Merge branch 'master' of github.com:CraZySacX/colorize

Conflicts:
	src/colorize.rs