Improve server discovery

[Schnouki]

From Trello:

An interesting problem keeps coming up on the Internet 2 conference call. Some of the universities on the call want to run buddycloud but, have deployed google apps onto their .edu domain. That means google is handling their XMPP server and there's no way to spin up buddycloud for their users and integrate with the existing XMPP names.

One solution I thought of was to run buddycloud on in-house-xmpp-server.bigEDU.edu and then use SRV discovery to point at something like: buddycloud-server.tcp.example.com. IN SRV 5 0 5269 inhouse-xmpp-server.bigEDU.edu.