Modify logic for saving webpage response data

- Call save_webpage before save_webpage_response in
  process_response_data
- Call save_webpage_redirects in save_webpage_response after building
  the @webpage_response and save @webpage_response after
- Change save_webpage_redirects to push new WebpageRedirect instances to the
  @webpage_response.webpage_redirects array
Remove unnecessary references to FactoryGirl
Change add_to_url_history callback to after_commit
Prefix before_action assignment methods with set_
Update @webpage_response variable after update