use Beeper fork of groupme API library

Signed-off-by: Sumner Evans <sumner@beeper.com>

example-config.yaml

@@ -9,7 +9,7 @@ homeserver:
 # Changing these values requires regeneration of the registration.
 appservice:
     # The address that the homeserver can use to connect to this appservice.
-    address: http://localhost:29318
+    address: http://localhost:29328
 
     # The hostname and port where this appservice should listen.
     hostname: 0.0.0.0