Add Data option to push. 

* bump to v.1.5
* Since dev changed significantly, had to refactor #88 into this version

@kitcambridge r?
Looks like we're accessing `sock.Uaid` in the `Serv` methods, too...maybe we should add a `PushWS.UAID()` method, and embed the `sync.RWMutex` into `PushWS` instead. `WorkWS.UAID()` could then just call `self.sock.UAID()`. Doesn't need to be part of this PR, though; just noting for the future.