Updated the suite of handler classes with documentation.

Updated XMLStream to return True or False from removeHandler to indicate if the handler
existed and was removed.

Waiter handlers now unregister themselves after timing out.

sleekxmpp/xmlstream/handler/xmlcallback.py

@@ -5,10 +5,32 @@
 
     See the file LICENSE for copying permission.
 """
-import threading
-from . callback import Callback
+
+from sleekxmpp.xmlstream.handler import Callback
+
 
 class XMLCallback(Callback):
-	
-	def run(self, payload, instream=False):
-		Callback.run(self, payload.xml, instream)
+
+    """
+    The XMLCallback class is identical to the normal Callback class,
+    except that XML contents of matched stanzas will be processed instead
+    of the stanza objects themselves.
+
+    Methods:
+        run -- Overrides Callback.run
+    """
+
+    def run(self, payload, instream=False):
+        """
+        Execute the callback function with the matched stanza's
+        XML contents, instead of the stanza itself.
+
+        Overrides BaseHandler.run
+
+        Arguments:
+            payload  -- The matched stanza object.
+            instream -- Force the handler to execute during
+                        stream processing. Used only by prerun.
+                        Defaults to False.
+        """
+        Callback.run(self, payload.xml, instream)