update_caps() can now do presence broadcasting.

As part of adding this feature:

    - fixed bug in update_caps() not assigning verstrings
    - fixed xep_0004 typo
    - can now use None as a roster key which will map to boundjid.bare
    - fixed using JID objects in disco node handlers
    - fixed failing test related to get_roster

Several of these bugs I've fixed before, so I either didn't push them
earlier, or I clobbered something when merging. *shrug*

tests/test_stream_roster.py

@@ -125,7 +125,8 @@ class TestStreamRoster(SleekTest):
         # Since get_roster blocks, we need to run it in a thread.
         t = threading.Thread(name='get_roster',
                              target=self.xmpp.get_roster,
-                             kwargs={str('callback'): roster_callback})
+                             kwargs={str('block'): False,
+                                     str('callback'): roster_callback})
         t.start()
 
         self.send("""