Add missing CommonActions#fill_in_signup_form method

This method allows to fill in CONSUL's signup form without interacting
with other UI elements, useful when using testing locales other than English

Backported from Decide Madrid

spec/support/common_actions.rb

@@ -12,4 +12,13 @@ module CommonActions
   include Users
   include Verifications
   include Votes
+
+  def fill_in_signup_form(email = 'manuela@consul.dev', password = 'judgementday')
+    fill_in 'user_username',              with: "Manuela Carmena #{rand(99999)}"
+    fill_in 'user_email',                 with: email
+    fill_in 'user_password',              with: password
+    fill_in 'user_password_confirmation', with: password
+    check 'user_terms_of_service'
+  end
+
 end