More work addressing review comments for Fernando's branch.

* :mod:`IPython.testing.globalipapp` now directly creates a
  :class:`~IPython.core.iplib.InteractiveShell` instance by passing it a
  configuration object, rather than creating an IPython application.
* Updated everything in :mod:`IPython.frontend` and :mod:`IPython.gui` to use
  raw :class:`~IPython.core.iplib.InteractiveShell directly rather than
  creating an IPython application.
* Updated the IPython sphinx extension to use raw
  :class:`~IPython.core.iplib.InteractiveShell directly rather than creating
  an IPython application.
* Removed code from :mod:`IPython.extensions.pretty` that called
  :func:`get_ipython` (r1271).
* Addressed comment on (r1284) about holding refs to deferreds in
  :mod:`IPython.kernel.ipclusterapp`.
* Removed :mod:`IPython.kernel` from list of modules tested by nose in
  :mod:`IPython.testing.iptest`. (r1318)

IPython/testing/iptest.py

@@ -343,9 +343,9 @@ def make_runners():
 
     # And add twisted ones if conditions are met
     if have['zope.interface'] and have['twisted'] and have['foolscap']:
-        # Note that we list the kernel here, though the bulk of it is
-        # twisted-based, because nose picks up doctests that twisted doesn't.
-        nose_pkg_names.append('kernel')
+        # We only list IPython.kernel for testing using twisted.trial as
+        # nose and twisted.trial have conflicts that make the testing system
+        # unstable.
         trial_pkg_names.append('kernel')
 
     # For debugging this code, only load quick stuff