Prevent update from directly PATCH request (Exercises 9.6.1)
open Gravatar change link with a new window
Added some test, which links are not appearing (Exercises 9.6.3)
Remove duplication in new.html.erb and edit.html.erb (Exercises 9.6.5)
Redirect to root page if user signed in (Exercises 9.6.6)
Exercises 9.6.8
Modify the destroy action to prevent admin users destorying themselves. (Exercises 9.6.9)