Run tests in pure mode as well.

.travis.yml

@@ -7,7 +7,10 @@ python:
 - "2.7_with_system_site_packages"
 - "3.4"
 - "pypy"
-script: PYTHONHASHSEED=random python setup.py test
+script:
+  - PYTHONHASHSEED=random python setup.py test
+  - make check-noextensions
 install:
   - sudo apt-get update
   - sudo apt-get install -qq git python-setuptools python-gevent python-fastimport python-mock
+  - sudo pip install unittest2