Update tostring methods.

Will now always show top-level namespace, unless it is the same
as the stream's default namespace. Also added the XMPP stream
namespace to the namespace map as 'stream'.

sleekxmpp/basexmpp.py

@@ -106,6 +106,7 @@ class BaseXMPP(XMLStream):
 
         self.default_ns = default_ns
         self.stream_ns = 'http://etherx.jabber.org/streams'
+        self.namespace_map[self.stream_ns] = 'stream'
 
         self.boundjid = JID("")
 
@@ -119,6 +120,8 @@ class BaseXMPP(XMLStream):
 
         self.sentpresence = False
 
+        self.stanza = sleekxmpp.stanza
+
         self.register_handler(
             Callback('IM',
                      MatchXPath('{%s}message/{%s}body' % (self.default_ns,