Update pytest from 3.2.5 to 3.3.0 (#404)

requirements.txt

@@ -6,7 +6,7 @@ flake8==3.4.1
 -e .[sa]
 sphinx==1.6.5
 tox==2.8.1
-pytest==3.2.5
+pytest==3.3.0
 pytest-cov==2.5.1
 pytest-sugar==0.9.0
 pytest-timeout==1.2.1