Support Haml through Calliope in View Layer

All that is needed is to start putting `*.haml` files in the templates folder and Calliope will pre-compile them into EEx strings. Actually, because of the way that it works you can mix and match Haml and EEx templates. 
@ericmj I'm actually having issues getting hex packages published. I changed machines and it won't let me authenticate now. I'm going to create an issue in hex but any ideas?