Move the handshake initialisation to the socket's onopen

This change moves the handshake initialisation to the socket's `onopen`.
This avoids us having to wait for a message from the server before
initiating the handshake, saving us half a round-trip. It should also
make it easier to eventually refactor out the legacy initialisation.

Author: Alec Gibson

lib/client/connection.js

@@ -141,6 +141,7 @@ Connection.prototype.bindToSocket = function(socket) {
 
   socket.onopen = function() {
     connection._setState('connecting');
+    connection._initializeHandshake();
   };
 
   socket.onerror = function(err) {
@@ -695,8 +696,8 @@ Connection.prototype._handleSnapshotFetch = function(error, message) {
 
 Connection.prototype._handleLegacyInit = function(message) {
   // If the minor protocol version has been set, we can ignore this legacy
-  // init message, and continue with the updated handshake protocol.
-  if (message.protocolMinor) return this._initializeHandshake();
+  // init message, and wait for a response to our handshake message.
+  if (message.protocolMinor) return;
   this._initialize(message);
 };