Add the start of a Fedmsg/GCM demo. Ish.

This goes along with the Fedmsg GCM Demo repo, but everything is
really bad and hacky right now.
Send the registration id to Sprunge for now.

When we switch to fedmsg-notifications and move everything to production
this will go away. Right now it's pretty hacky. You end up having to
set up the fedmsg-gcm-demo daemon locally, getting an "Sender ID" from the
Google API console, typing that into Fedora Mobile, and then getting a
"Registration ID" back in the form of a sprunge.us link. Once you have that,
you have to copy it into a YAML file.

This is hugely a proof of concept, just because I want to be able to demo this
stuff at Flock in August.