Add tests & actually chat.

Add command line params. Yay! It’s hacky and dumb (fixed pos— server
then password, no support for port or channels), but it works for
testing.
Add tests.
Don’t try to wait for welcome messages for now.
Simplify message loop.
Simplify irc-connect somewhat.
Add ping handler, handler for PRIVMSG, and a general printing one for
console convenience.

May not be working. It’s late. :(