Fix/70 server callback and promise

[andrewshatnyy]

• add node style callback to server server.start(function(err) {...});
• add a promise server.start().then(success, error);

[diversario]

Thanks for the PR!

Two things: 1) Please use Bluebird for Promises, 2) Please add the promise interface to SsdpClient#start (it takes callback already).

[andrewshatnyy]

Sure on it. Tests are failing due to unrelated reasons...