Update XEP-0085 plugin to work with both ElementTree and cElementTree

Each state element must have its own stanza class now. A stanza class
with an empty name field causes errors in ElementTree, even though
it works fine with cElementTree.

sleekxmpp/plugins/xep_0085/chat_states.py

@@ -37,7 +37,11 @@ class xep_0085(base_plugin):
                          StanzaPath('message@chat_state=%s' % state),
                          self._handle_chat_state))
 
-        register_stanza_plugin(Message, ChatState)
+        register_stanza_plugin(Message, stanza.Active)
+        register_stanza_plugin(Message, stanza.Composing)
+        register_stanza_plugin(Message, stanza.Gone)
+        register_stanza_plugin(Message, stanza.Inactive)
+        register_stanza_plugin(Message, stanza.Paused)
 
     def post_init(self):
         base_plugin.post_init(self)

sleekxmpp/plugins/xep_0085/stanza.py

@@ -71,3 +71,23 @@ class ChatState(ElementBase):
             if state_xml is not None:
                 self.xml = ET.Element('')
                 parent.xml.remove(state_xml)
+
+
+class Active(ChatState):
+    name = 'active'
+
+
+class Composing(ChatState):
+    name = 'composing'
+
+
+class Gone(ChatState):
+    name = 'gone'
+
+
+class Inactive(ChatState):
+    name = 'inactive'
+
+
+class Paused(ChatState):
+    name = 'paused'