Stop bundling the numpydoc Sphinx extension

numpydoc is now a separately installable package, so we can express a
dependency for the 'doc' install option, rather than bundling it. This
gets us bugfixes that our copy was lacking - one of which was causing a
problem for the ShiningPanda docs job.

setup.py

@@ -275,7 +275,7 b" if 'setuptools' in sys.modules:"
         parallel = 'pyzmq>=2.1.11',
         qtconsole = ['pyzmq>=2.1.11', 'pygments'],
         zmq = 'pyzmq>=2.1.11',
-        doc = 'Sphinx>=0.3',
+        doc = ['Sphinx>=0.3', 'numpydoc'],
         test = 'nose>=0.10.1',
         notebook = ['tornado>=3.1', 'pyzmq>=2.1.11', 'jinja2'],
         nbconvert = ['pygments', 'jinja2', 'Sphinx>=0.3']