Update ping_timeout documented default to accord with current Engine.IO behavior (#1255)

Author: lucaswiman

src/socketio/async_server.py

@@ -64,7 +64,7 @@ class AsyncServer(base_server.BaseServer):
                           is a grace period added by the server.
     :param ping_timeout: The time in seconds that the client waits for the
                          server to respond before disconnecting. The default
-                         is 5 seconds.
+                         is 20 seconds.
     :param max_http_buffer_size: The maximum size of a message when using the
                                  polling transport. The default is 1,000,000
                                  bytes.

src/socketio/server.py

@@ -73,7 +73,7 @@ class Server(base_server.BaseServer):
                           is a grace period added by the server.
     :param ping_timeout: The time in seconds that the client waits for the
                          server to respond before disconnecting. The default
-                         is 5 seconds.
+                         is 20 seconds.
     :param max_http_buffer_size: The maximum size of a message when using the
                                  polling transport. The default is 1,000,000
                                  bytes.