Initial Development

Would be good to have some additional tests for:

 - Template overrides (or passing a Handlebars template if you go that route)
 - Passing a jQuery element vs. a DOM selector
 - Event emitter
 - async = false 

Not sure about the strategy of making real requests to the actual APIs, one thing that precludes you from is subscribing new emails. Mocking them with just the bare minimum required to reproduce the success/failure scenarios in each API would probably be better. Any thoughts/advice here @joanniclaborde?