We were inconsistent on this one. I consider it particularly useful when
a method starts with a `return` statement.
In other cases, we probably shouldn't have a guard rule in the middle of
a method in any case, but that's a different refactoring.
changed functions on verification.rb, the first thing they do is
return true whene skip_user_verification is active.
changed show_welcome_screen? on user.rb, now its shows the welcome
page even with te option active.
changed welcome.html.erb, now if the user see this view and the
option is activated, all 4 checks are green, not only 2.
