Fix compatibility issue with Paho MQTT 1.3.0.

Author: jburhenn

cayenne/client.py

@@ -34,7 +34,7 @@
 
 
 # The callback for when the client receives a CONNACK response from the server.
-def on_connect(client, cayenne, rc):
+def on_connect(client, cayenne, flags, rc):
     if rc != 0:
         # MQTT broker error codes
         broker_errors = {

setup.py

@@ -36,6 +36,6 @@
       classifiers      = classifiers,
       packages         = ['cayenne'],
       install_requires = [
-        'paho-mqtt',
+        'paho-mqtt >= 1.0',
       ],
       )