Add a couple Jabber control/debug scripts

* `jabber_passwd` will allow users to
    * create new accounts
    * change passwords on existing accounts
* `jabber_send` will allow users to send messages from the command line.
    * This should greatly help debugging when things go wrong.

Both scripts will print usage instructions when executed.
Use the puppet ruby interpreter

This is bad practice as a whole, but works for the classroom
environment.
Add interpreter disclaimer

Just in case people take these home and use them as code inspiration.