Add draft docs for building the docs

docs/documenters/buildthedocs.rst

+Building the Docs Locally
+=========================
+
+You will need:
+
+#. Git
+#. Python and Virtualenv
+#. Make
+
+To build the docs:
+
+#. ``git clone https://github.com/hypothesis/client.git``
+#. ``cd client``
+#. Create and activate a Python virtual environment.
+#. ``pip install -r requirements-dev.in``
+#. ``make docs``
+
+Now open http://localhost:8888 to view your local build of the docs.
+The built docs will automatically update when you save changes to the source
+files.

docs/documenters/index.rst

+For Documenters
+===============
+
+This section contains documentation for **documenters** who want to contribute
+documentation to the Hypothesis client.
+
+.. toctree::
+   :maxdepth: 3
+
+   buildthedocs

docs/index.rst

@@ -15,3 +15,4 @@ It's used by the
 
    publishers/index
    developers/index
+   documenters/index