CLI tool to access zulip

You must create a zulip.toml file with the following contents

email="zulip email (often your github email)"
key="API key from your zulip settings"
site="rust-lang.zulipchat.com"

Then invoke zulip streams to cache all the streams and use zulip mentions to get an ordered list of the topics sorted in order of when you were last pinged in them.