#25 Some keys do not work properly on some platforms

[ichigo-0]

The problem basically is that the event handling code sometimes uses event.key.keysym.unicode in cases where it should use event.key.keysym.sym instead. Keys that I've noticed being problematic on this computer (a Mac) include: backspace, delete, the arrow keys, all the Fn keys, insert, home, end, page up, and page down.

I've attached a patch that should fix this, though since other keys might cause problems on other systems, you might consider a more general solution such as only using keysym.unicode when it is a printable ascii character (between 0x20 and 0x7e).