adjust contribution guide to mention spell check. refs #166

Author: dbu

doc/contributing.rst

@@ -1,6 +1,10 @@
 Contributing
 ============
 
+We are happy for contributions. Before you invest a lot of time however, best
+open an issue on github to discuss your idea. Then we can coordinate efforts
+if somebody is already working on the same thing.
+
 Testing the Library
 -------------------
 
@@ -27,7 +31,7 @@ To run the unit tests separately:
 Functional Tests
 ~~~~~~~~~~~~~~~~
 
-The library also includes functional tests against a Varnish and NGINX instance. 
+The library also includes functional tests against a Varnish and NGINX instance.
 The functional test suite by default uses PHP’s built-in web server. If you have
 PHP 5.4 or newer, simply run with the default configuration.
 
@@ -44,8 +48,8 @@ To run the functional tests:
 
     $ phpunit tests/Functional
 
-Tests are organized in groups: one for each reverse proxy supported. At the moment 
-groups are: `varnish` and  `nginx`. 
+Tests are organized in groups: one for each reverse proxy supported. At the moment
+groups are: `varnish` and  `nginx`.
 
 To run only the `varnish` functional tests:
 
@@ -58,21 +62,22 @@ For more information about testing, see :doc:`/testing-your-application`.
 Building the Documentation
 --------------------------
 
-First `install Sphinx`_, then download the requirements: 
+First `install Sphinx`_ and `install enchant`_ (e.g. ``sudo apt-get install enchant``),
+then download the requirements:
 
 .. code-block:: bash
 
     $ pip install -r doc/requirements.txt
-    
+
 To build the docs:
 
 .. code-block:: bash
 
     $ cd doc
     $ make html
+    $ make spelling
 
 .. _HHVM: http://www.hhvm.com/
 .. _HHVM FastCGI server: https://github.com/facebook/hhvm/wiki/fastcgi
 .. _install Sphinx: http://sphinx-doc.org/latest/install.html
-
-
+.. _install enchant: http://www.abisource.com/projects/enchant/