Make the default connection timeout None

This fixes the default behavior, which used to cause a socket timeout
when waiting for 10 seconds for a message to be produced.

Author: rdiomar

kafka/conn.py

@@ -17,8 +17,13 @@ class KafkaConnection(local):
     by a call to `recv` in order to get the correct response. Eventually,
     we can do something in here to facilitate multiplexed requests/responses
     since the Kafka API includes a correlation id.
+
+    host:    the host name or IP address of a kafka broker
+    port:    the port number the kafka broker is listening on
+    timeout: default None. The socket timeout for sending and receiving data.
+             None means no timeout, so a request can block forever.
     """
-    def __init__(self, host, port, timeout=10):
+    def __init__(self, host, port, timeout=None):
         super(KafkaConnection, self).__init__()
         self.host = host
         self.port = port