Travis py33 (#69)

Fix Travis tests for Python 3.3

Failure was caused by installing batchspawner too early, resulting in
current version Jupyterhub libraries being installed by pip before the
checked-out version could be installed.

Author: mbmilligan

.travis.yml

@@ -28,8 +28,9 @@ before_install:
 install:
 # Don't let requirements pull in tornado 5 yet except for jupyterhub master
     - if [ $JHUB_VER != "master" ]; then pip install "tornado<5.0"; fi
-    - pip install --pre -f travis-wheels/wheelhouse -r jupyterhub/dev-requirements.txt .
+    - pip install --pre -f travis-wheels/wheelhouse -r jupyterhub/dev-requirements.txt
     - pip install --pre -e jupyterhub
+
 script:
     - travis_retry py.test --lf --cov batchspawner batchspawner/tests -v
 #after_success: