Update quick start guide for start_default

Author: peterbarker

docs/guide/quick_start.rst

@@ -46,18 +46,16 @@ we then use to query the attributes.
 .. code:: python
 
     print "Start simulator (SITL)"
-    from dronekit_sitl import SITL
-    sitl = SITL()
-    sitl.download('copter', '3.3', verbose=True)
-    sitl_args = ['-I0', '--model', 'quad', '--home=-35.363261,149.165230,584,353']
-    sitl.launch(sitl_args, await_ready=True, restart=True)
+    import dronekit_sitl
+    sitl = dronekit_sitl.start_default()
+    connection_string = sitl.connection_string()
 
     # Import DroneKit-Python
     from dronekit import connect, VehicleMode
 
     # Connect to the Vehicle. 
-    print "Connecting to vehicle on: 'tcp:127.0.0.1:5760'"
-    vehicle = connect('tcp:127.0.0.1:5760', wait_ready=True)
+    print("Connecting to vehicle on: %s" % (connection_string,))
+    vehicle = connect(connection_string, wait_ready=True)
 
     # Get some vehicle attributes (state)
     print "Get some vehicle attribute values:"