README: add note about python version compatibility

README.md

@@ -1,2 +1,14 @@
-This is client side implementation of Qubes management API. See
+This is client side implementation of Qubes Admin API. See
 https://www.qubes-os.org/doc/mgmt1/ for protocol specification.
+
+
+
+Compatibility
+=============
+
+Most of the API modules are compatible with Python >= 2.7.
+Very few parts require Python >= 3.4:
+ - tools (`qvm-*`)
+ - qubesmgmt.events module (for asyncio module)
+
+Parts not compatible with Python < 3.4, are not installed in such environment.