0.4: Moves from cassie to pinky.

This means asynchronous tasks now can just return a Promises/a+ compliant
Thenable interface and it'll Just Work™. Not to mention we can leverage the
combinators written for the pinky library and make things more composable.

Later, a rewrite of I/O actions using ffs can be done. This will make things
slower synchronous, but faster for things like `watch`. Also, this would allow
daemonising at some point.