pass callback function to cmd.update()
remove obsolete autoarchive functionality
edge cases for Command.update callbacks
unit tests for command update callback
ensure cli.setprompt continuation called last

not tested :(

also ignore the last chunk that's part of the next patch but I'm
dogfooding lush and it doesn't support interactive terminal yet

-_- TODO
use deferreds for syncing prompt to commands

fixes hraban/lush#31
increase size of terminal (80 chars wide)

fixes hraban/lush#41
cancel stream widget drop-down plans

this was a stupid UI to begin with glad I didn't spend time implementing
it