adds spec step to confirm email after sign up

rel: #44

spec/features/users_spec.rb

@@ -15,6 +15,11 @@ feature 'Users' do
     click_button 'Sign up'
 
     expect(page).to have_content "A message with a confirmation link has been sent to your email address. Please follow the link to activate your account."
+
+    sent_token = /.*confirmation_token=(.*)".*/.match(ActionMailer::Base.deliveries.last.body.to_s)[1]
+    visit user_confirmation_path(confirmation_token: sent_token)
+
+    expect(page).to have_content "Your email address has been successfully confirmed"
   end
 
   scenario 'Sign in' do