python is able to import modules from a zip file. if the zip file
contains __main__.py it will even run it as a script! this lets us bundle
bbj's frontend together with its sole external dependency (urwid) to
create a single executable file that'll run anywhere with python
installed, no virtualenv needed.
the only downside is that python can't import shared objects (.so) from a
zip file, so urwid can't use its C-accelerated str_util module and has
to fall back to the python version. which is slower, probably.
