Fixed headers in docs
diff --git a/docs/contributing.rst b/docs/contributing.rst
index 4647818..934bb45 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -48,7 +48,7 @@
from __future__ import absolute_import, division, print_function
C bindings
-----------
+~~~~~~~~~~
When binding C code with ``cffi`` we have our own style guide, it's pretty
simple.
@@ -161,7 +161,7 @@
You are now ready to run the tests and build the documentation.
Running Tests
--------------
+~~~~~~~~~~~~~
``cryptography`` unit tests are found in the ``tests/`` directory and are
designed to be run using `pytest`_. `pytest`_ will discover the tests
@@ -195,7 +195,7 @@
will see one or more ``InterpreterNotFound`` errors.
Building Documentation
-----------------------
+~~~~~~~~~~~~~~~~~~~~~~
``cryptography`` documentation is stored in the ``docs/`` directory. It is
written in `reStructured Text`_ and rendered using `Sphinx`_.