Make append works on more screen type like PM::TableScreen, 

In order to make append syntax works on all type of ProMotion Screen, like PM::TableScreen, it should be extend under ProMotion::ScreenModule not just ProMotion::Screen. Because all type of ProMotion screens are `include ProMotion::ScreenModule`.

I am try to write some test file, but I think the old test for PM::Screen should works. If it pass, it should be works well on other type of screen, like PM::TableScreen.

Please look at those link:
https://github.com/clearsightstudio/ProMotion/wiki/Guide:-Making-Your-Own-Screens
https://github.com/clearsightstudio/ProMotion/blob/master/lib/ProMotion/screen/screen.rb#L5
https://github.com/clearsightstudio/ProMotion/blob/master/lib/ProMotion/table/table_screen.rb#L3
https://github.com/clearsightstudio/ProMotion-form/blob/master/lib/ProMotion/form/form_screen.rb#L3