Automatically reconnect (by default) - Rename socket events

 * Connect callback passed to the connect() function - Will be called
   automatically each time the connection is established.
 * ddp will automatically reconnect when the connection is closed
 * opts.auto_reconnect and opts.auto_reconnect_timer can be set to change the
   default reconnect behaviour
 * ddp emits `socket-error` and `socket-close` when an error or a close occurs