Since the botserver can be run directly after installation via pip,
and only supports Python 3, we definitely want the explicit shebang
lines there.
We only don't want this in zulip/, which supports Python 2+3.
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.
doc.md better describes the style of documentation that will live
inside these files, since we want these to be similar to our
webhooks' doc.md files in terms of how these are rendered and
composed of Markdown macros.
