More accurate matching of the CSS string passed to init().
Preserve callback methods that are already set. Fixes #40.
Merge branch 'master' into slave

Conflicts:
	gm_config.js

Resolved:
	Manual edit to match upstream.
	Similar fix match from NodeUndefined branch via https://github.com/Martii/GM_config/commit/f08ecdd32d6339f94151bcb74a255c5a571d8734