Update client.py to post to groups (Issue #63)

Jut followed the recipe in the issue

fbchat/client.py

@@ -264,15 +264,14 @@ class Client(object):
             'manual_retry_cnt' : '0',
             'signatureID' : getSignatureID(),
             'has_attachment' : image_id != None,
-            'other_user_fbid' : recipient_id,
             'specific_to_list[0]' : 'fbid:' + str(recipient_id),
             'specific_to_list[1]' : 'fbid:' + str(self.uid),            
 
         }
-
-
-        
-
+        if message_type.lower() == 'group':
+            data["thread_fbid"] = recipient_id 
+        else:
+            data["other_user_fbid"] = recipient_id
 
         if image_id:
             data['image_ids[0]'] = image_id