add a master branch to cdn

Right now, master is never deployed to the CDN. Only version tags are deployed.

However, it would be handy to be able to deploy code to the CDN without actually doing a release. For example, right now, I'd like to deploy a version that was easily reviewable by a distributed developer. However, it's 4:39pm on a friday and I don't want to doing a release that hits sites.

This should only be used for testing purposes and people should never use this version in production.