use common conventions in Client class

[boneskull]

Currently, to know when the Client class has connected, a user will pass an onSuccess callback to the constructor.

It would be best if the Client class' API was more familiar. There's no reason that I can see that this class must deviate from common convention, which has been established by Node.js. Ideally:

• Client should be an EventEmitter
• Client should emit connected and other events similarly to net.Socket
• The constructor should have a signature similar to net.createConnection
• A factory function should be exposed so that the user needn't use the new keyword; alternatively, check for this in constructor and return a newly constructed object if falsy

This is obviously a breaking change and would necessitate a major version bump.