This commit was originally from @fredfishgames, but it
needed a big rebase due to use letting it sit too long.
Also, we decided not to have shebangs at the top of test
files.
This program replaces zulip_bot_output.py, which had
gotten a little out of date.
It should be able to simulate a terminal conversation for
all of our bots, including those that use "advanced" features:
third party config files: tested with giphy
message updates: tested with incrementor
storage: tested with virtual_fs and others
