Release 1.2.3

* dtls/wrapper.py: Add optional parameter to DtlsSocket:
    client_timeout (seconds). If client_timeout is specified,
    clients that have not communicated within the time frame
    will be dropped.
  * setup.py: Version incremented to 1.2.3
  * dtls/__init__.py: Increment version

dtls/__init__.py

@@ -32,7 +32,7 @@ sockets.
 wrap_socket's parameters and their semantics have been maintained.
 """
 
-VERSION = 1, 2, 2
+VERSION = 1, 2, 3
 
 def _prep_bins():
     """