#112 Default shell- and open-commands flags

Maybe something like this: ait -S qs -O qs where -S means default shell-command and -O means default open-command. This would make it so that you could use something like scripts/qs and not have to type it in the first time. In other words, when you use esc x for the first time it would show (default qs).

This might just be dumb and might just be better to have a command history instead...

Maybe it might be nicer to have a history file that gets placed somewhere? $HOME/.local/share/ait/history? Maybe just $HOME/.ait-history? It would likely be easier to do command line options, however.

leaning towards the command line options so that ait doesn't leave crap all over the place.

Blocked by #113