MAINT: update ReST formatting in README.

Related to missing README content on
https://pypi.python.org/pypi/numpydoc/0.7.0

Doesn't help fix that, but at least this file now looks like valid ReST.

Author: rgommers

README.rst

@@ -11,15 +11,15 @@ of them in third-party projects.
 
 The following extensions are available:
 
-  - ``numpydoc``: support for the Numpy docstring format in Sphinx, and add
-    the code description directives ``np:function``, ``np-c:function``, etc.
-    that support the Numpy docstring syntax.
+- ``numpydoc``: support for the Numpy docstring format in Sphinx, and add
+  the code description directives ``np:function``, ``np-c:function``, etc.
+  that support the Numpy docstring syntax.
 
-  - ``numpydoc.traitsdoc``: For gathering documentation about Traits attributes.
+- ``numpydoc.traitsdoc``: For gathering documentation about Traits attributes.
 
-  - ``numpydoc.plot_directive``: Adaptation of Matplotlib's ``plot::``
-    directive. Note that this implementation may still undergo severe
-    changes or eventually be deprecated.
+- ``numpydoc.plot_directive``: Adaptation of Matplotlib's ``plot::``
+  directive. Note that this implementation may still undergo severe
+  changes or eventually be deprecated.
 
 See `A Guide to NumPy/SciPy Documentation <https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt>`_
 for how to write docs that use this extension.
@@ -36,30 +36,30 @@ Options
 
 The following options can be set in conf.py:
 
-- numpydoc_use_plots: bool
+- ``numpydoc_use_plots``: bool
 
   Whether to produce ``plot::`` directives for Examples sections that
   contain ``import matplotlib``.
 
-- numpydoc_show_class_members: bool
+- ``numpydoc_show_class_members``: bool
 
   Whether to show all members of a class in the Methods and Attributes
   sections automatically.
   ``True`` by default.
 
-- numpydoc_show_inherited_class_members: bool
+- ``numpydoc_show_inherited_class_members``: bool
 
   Whether to show all inherited members of a class in the Methods and Attributes
   sections automatically. If it's false, inherited members won't shown.
   ``True`` by default.
 
-- numpydoc_class_members_toctree: bool
+- ``numpydoc_class_members_toctree``: bool
 
   Whether to create a Sphinx table of contents for the lists of class
   methods and attributes. If a table of contents is made, Sphinx expects
   each entry to have a separate page.
   ``True`` by default.
 
-- numpydoc_edit_link: bool  (DEPRECATED -- edit your HTML template instead)
+- ``numpydoc_edit_link``: bool  (DEPRECATED -- edit your HTML template instead)
 
   Whether to insert an edit link after docstrings.