Three original styles: Helium, Selenium, Stygium.

Stygium is a very basic black theme, even simpler
and darker than Carbon.
Selenium uses deep blue colors, while Helium
has a spectrum of several light pastels.
Remove superfluous arg from /quit command.
Added /list command (fixes #13).

The /list command will query the server
for available rooms, and print out a list
of links that can be used to immediately join them.
Added /who command (fixes #14).

The /who command queries what users are
in a given channel.

Unfortunately, due to XMPP's insanely compartmentalized
room structure, it is basically impossible to get extensive
information about rooms you are not currently in.
Even in the current room, this query will reveal less
information than the roster contains - only nick, no status,
no full address, no roles, etc.

Therefore, when querying /who in the current room, we don't
bother with a server request, but simply print the current roster.

When querying /who in a different room, we print out what little
information the server returns.