chore(closure-compiler): update closure compiler to 2013-02-07

custom compiled compiler at r4796bc81
chore(Rakefile): enable type-checking during closure compilation

currently only for angular.js, more to come
chore(*): adds or fixes closure type annotations

This change resolves all warnings found by the closure compiler
when verbose mode is turned on and all the other flags remain at defaults.

Part of this commit contains code contributed by Ben McCann via PR #1710.