feat(build): Add grunt-ngmin for annotation

Unfortunately, grunt-ngmin is still in an early state right now and can't handle the fancy way ng-boilerplate does module declaration (with the `.config` `.controller` etc functions called on a seperate line from the module declaration), so it doesn't work yet.  Still, it could stay in a branch for now until ngmin matures.  Or we can be more verbose with declaration of things (it does work if we put `angular.module('module')` before every call).