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/xmlwaiter.py

@@ -5,9 +5,29 @@
 
     See the file LICENSE for copying permission.
 """
-from . waiter import Waiter
+
+from sleekxmpp.xmlstream.handler import Waiter
+
 
 class XMLWaiter(Waiter):
-	
-	def prerun(self, payload):
-		Waiter.prerun(self, payload.xml)
+
+    """
+    The XMLWaiter class is identical to the normal Waiter class
+    except that it returns the XML contents of the stanza instead
+    of the full stanza object itself.
+
+    Methods:
+        prerun -- Overrides Waiter.prerun
+    """
+
+    def prerun(self, payload):
+        """
+        Store the XML contents of the stanza to return to the
+        waiting event handler.
+
+        Overrides Waiter.prerun
+
+        Arguments:
+            payload -- The matched stanza object.
+        """
+        Waiter.prerun(self, payload.xml)