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. 
Do you get an error message? If you haven't created a local API key you have to create it with `mix hex.key new -u username -p password` or pass the `-u` and `-p` flags to `mix hex.publish`.