Need to make a copy of the passed in hash.

  * env.delete "SAUCE_ONDEMAND_BROWSERS" was
	deleting the SAUCE_ONDEMAND_BROWSERS environment variable which
	had ripple effects and negative consequences for code expecting
	it to be there.
Merge pull request #230 from LessonPlanet/fix-config-to-not-delete-from-env

Fix config to not delete from ENV