Configurable Keybindings

Hi mattn,

I really dislike the keybindings in the calendar window itself, so I sat down and made them configurable. Moreover, I incorporated the changes of csexton that remove the trailing ws in the calendar window, because that's really annoying having a plugin like FixWhitespace installed. 

I don't know if you're interested in the keybinding-change, but if you are, I would be glad to contribute.

tc