users: lock out users with invalid names until they change their name.

Forcibly redirect users to the name change page if their name is
invalid. This means user with invalid names can't do anything or view
any pages until they change their name. API requests are still allowed.

app/controllers/user_name_change_requests_controller.rb

@@ -3,6 +3,8 @@
 class UserNameChangeRequestsController < ApplicationController
   respond_to :html, :json, :xml
 
+  skip_before_action :redirect_if_name_invalid?
+
   def new
     @change_request = authorize UserNameChangeRequest.new(permitted_attributes(UserNameChangeRequest))
     respond_with(@change_request)