Send signup confirmation emails

Not much done in the code itself yet, but I have set up a Mandrill account with (currently fairly barren) templates for the CSOL signup and <13 CSOL signup emails based on the copy at

http://etherpad.mozilla.org/jessie

The key for the Mandrill account I'm using is g4NM4C1BRDl44wfUdTqHIQ.  Setting CSOL_MANDRILL_KEY to this value will use the templates I've created.