Allow pasting when using views/app.go

[chrBrd]

At present it doesn't seem possible to handle pasting events when using the Application view. The Screen passed to the SetScreen() method should, as far as I can tell, be uninitialised, but calling the EnablePaste() method on an uninitialised screen will segfault when TPuts() is called due to t.tty being nil.

As the Application view is effectively a very handy convenience wrapper then being able to support pasting while using it would be appreciated.