Added version compatibility chart to docs #nolog

Author: miguelgrinberg

docs/intro.rst

@@ -15,6 +15,32 @@ web browsers) and a server. The official implementations of the client
 and server components are written in JavaScript. This package provides
 Python implementations of both, each with standard and asyncio variants.
 
+Version compatibility
+---------------------
+
+The Socket.IO protocol has been through a number of revisions, and some of these
+introduced backward incompatible changes, which means that the client and the
+server must use compatible versions for everything to work.
+
+If you are using the Python client and server, the easiest way to ensure compatibility
+is to use the same version of this package for the client and the server. If you are
+using this package with a different client or server, then you must ensure the
+versions are compatible.
+
+The version compatibility chart below maps versions of this package to versions
+of the JavaScript reference implementation and the versions of the Socket.IO and
+Engine.IO protocols.
+
++------------------------------+-----------------------------+-----------------------------+-------------------------+
+| JavaScript Socket.IO version | Socket.IO protocol revision | Engine.IO protocol revision | python-socketio version |
++==============================+=============================+=============================+=========================+
+| 0.9.x                        | 1, 2                        | 1, 2                        | Not supported           |
++------------------------------+-----------------------------+-----------------------------+-------------------------+
+| 1.x and 2.x                  | 3, 4                        | 3                           | 4.x                     |
++------------------------------+-----------------------------+-----------------------------+-------------------------+
+| 3.x                          | 5                           | 4                           | 5.x                     |
++------------------------------+-----------------------------+-----------------------------+-------------------------+
+
 Client Examples
 ---------------