Added implementation and tests for XEP-0085 - Chat State Notifications.

Chat states may be set using:

msg['chat_state'].active()
msg['chat_state'].composing()
msg['chat_state'].gone()
msg['chat_state'].inactive()
msg['chat_state'].paused()

Checking a chat state can be done with either:

msg['chat_state'].getState()
msg['chat_state'].name

When a message with a chat state is receieved, the following events
may occur:

chatstate_active
chatstate_composing
chatstate_gone
chatstate_inactive
chatstate_paused

where the event data is the message stanza. Note that currently these
events are also triggered for messages sent by SleekXMPP, not just those
received.

tests/test_chatstates.py

@@ -0,0 +1,47 @@
+import unittest
+from xml.etree import cElementTree as ET
+from sleekxmpp.xmlstream.matcher.stanzapath import StanzaPath
+from . import xmlcompare
+
+import sleekxmpp.plugins.xep_0085 as cs
+
+def stanzaPlugin(stanza, plugin):                                                                       
+	stanza.plugin_attrib_map[plugin.plugin_attrib] = plugin                                             
+	stanza.plugin_tag_map["{%s}%s" % (plugin.namespace, plugin.name)] = plugin 
+
+class testchatstates(unittest.TestCase):
+
+	def setUp(self):
+		self.cs = cs
+		stanzaPlugin(self.cs.Message, self.cs.Active)
+		stanzaPlugin(self.cs.Message, self.cs.Composing)
+		stanzaPlugin(self.cs.Message, self.cs.Gone)
+		stanzaPlugin(self.cs.Message, self.cs.Inactive)
+		stanzaPlugin(self.cs.Message, self.cs.Paused)
+
+	def try2Methods(self, xmlstring, msg):
+		msg2 = self.cs.Message(None, self.cs.ET.fromstring(xmlstring))
+		self.failUnless(xmlstring == str(msg) == str(msg2), 
+				"Two methods for creating stanza don't match")
+        
+	def testCreateChatState(self):
+		"""Testing creating chat states."""
+		xmlstring = """<message><%s xmlns="http://jabber.org/protocol/chatstates" /></message>"""
+
+		msg = self.cs.Message()
+		msg['chat_state'].active()
+		self.try2Methods(xmlstring % 'active', msg)
+
+		msg['chat_state'].composing()
+		self.try2Methods(xmlstring % 'composing', msg)
+
+		msg['chat_state'].gone()
+		self.try2Methods(xmlstring % 'gone', msg)
+
+		msg['chat_state'].inactive()
+		self.try2Methods(xmlstring % 'inactive', msg)
+
+		msg['chat_state'].paused()
+		self.try2Methods(xmlstring % 'paused', msg)
+
+suite = unittest.TestLoader().loadTestsFromTestCase(testchatstates)