added docs testing to tox

Author: masci

tox.ini

@@ -1,5 +1,9 @@
 [tox]
-envlist = py26-django14,py26-django15,py26-django16,py27-django14,py27-django15,py33-django15,py27-django16,py33-django16
+envlist =
+    py26-django14, py26-django15, py26-django16,
+    py27-django14, py27-django15, py27-django16,
+    py33-django15, py33-django16,
+    docs
 
 [testenv]
 downloadcache = {toxworkdir}/cache/
@@ -54,3 +58,9 @@ basepython = python3.3
 deps =
     https://www.djangoproject.com/download/1.6b4/tarball/
     {[testenv]deps}
+
+[testenv:docs]
+basepython=python
+changedir=docs
+deps=sphinx
+commands=make html