Consistent, configurable logging in the JavaScript client

[analogrelay]

The JavaScript client (and indeed all the clients) needs to have configurable logging rather than just relying on console.log as it does right now.

[moozzyk]

This was originally being tracked here: #3 but a separate issue makes it more visible.

[moozzyk]

#484 (comment)

[muratg]

For alpha1: add ability to turn off console.log lines (for node.js usage).

In the next milestone we'll design/implement the right abstraction for client side logging.

[muratg]

@moozzyk will also look into adding an options object at the HubConnection class. We want to have a bool value for logging, a logger object and hub protocol.

[moozzyk]

Fixed in: e4c1b88 and 7db480b