fix(connection): don't require parameters for address on open

Some potential future user-implemented transport might use an
address that doesn't have a host or port at all (perhaps a named
pipe), so it doesn't make sense for us to require these properties
exist.

lib/connection.js

@@ -316,7 +316,6 @@ Connection.ErrorReceived = 'connection:errorReceived';
  * @param sasl      If given, contains a "negotiate" method that, given address and a callback, will run through SASL negotiations.
  */
 Connection.prototype.open = function(address, sasl) {
-  u.assertArguments(address, ['protocol', 'host', 'port']);
   this.connSM.connect(address, sasl);
 };