Add a chat service to the notebook

[mpatel]

Features:

• Visit  #sage-devel, say, from a worksheet.
• Create, join, and send invites to ad hoc [private] chatrooms managed by a notebook server.

A prime candidate is  qwebirc. Apparently, this is the backend for  Freenode's own  webchat client.

[mpatel]

There's a jsMath-enabled  qwebirc at

•  http://sage.math.washington.edu/home/mpatel/projects/sagenet

To test the server, unpack the archive, run run.py, visit

•  http://sage.math.washington.edu:9090/?channels=sage-devel

join the channel, and enter $\alpha$, say.