Created admin interface to create new category

* Dashboard admin view uses _category partial
* Added validations for location and category models
* Deleted duplicate sign-in/sign-out links in layout
* Modified category index view to delete create category form section
take a look at the law of demeter http://devblog.avdi.org/2011/07/05/demeter-its-not-just-a-good-idea-its-the-law/

More or less, don't call email through user. `@dashboard.user_email`