Race conditions when reconnecting

[lgrahl]

A WebSocket close is not immediate. We should return a Promise, wait for the close event and then resolve. However, the main problem is that we allow to .connect immediately after a .disconnect which results in racy behaviour as both WebSocket connections are bound to the same event handlers.

This would be a major change and requires significant refactoring. For now, applications should always either:

1. Wait for the connection-closed event, or
2. Unbind all events after a .disconnect, throw the SaltyRTC instance away and create a new one. Even if you do this, be prepared to see log messages from previous connections (I'm working on removing this).