Add more explicit example of how to register custom passes and warnings guards.
Add more explicit example of how to register custom passes and warnings guards.

mihaip/react-closure-compiler,j0sh/react-closure-compiler,mihaip/react-closure-compiler,j0sh/react-closure-compiler,rgpower/react-closure-compiler,j0sh/react-closure-compiler,mihaip/react-closure-compiler,rgpower/react-closure-compiler