place outer most key buttons all the way at the edge of the screen

In order to make the input experience better, I think it would help to place buttons like "q" and "p" or "shift" and "backspace" that are almost at the very edge of the screen, all the way at the edge - just like the number selector and Enter key already are.

This would avoid some "missed" keys if one taps at the very edge.

somewhat related to #179 (moved)