Add docs to travis build

.travis.yml

@@ -8,6 +8,8 @@ matrix:
           env: TOXENV=cover
         - python: 3.5
           env: TOXENV=cover3
+        - python: 3.5
+          env: TOXENV=docs
         - python: 2.6
           env: TOXENV=py26
         - python: 2.7

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    cover,cover3,py26,py27,py32,py33,py34,py35,pypy,docs
+    cover,cover3,docs,py26,py27,py32,py33,py34,py35,pypy
 
 [testenv]
 deps =