pin casperjs to 1.1.1

last known-good version to run 4.x tests

.travis.yml

@@ -18,7 +18,7 @@ env:
     - GROUP=js/services
     - GROUP=js/tree
 before_install:
-    - 'if [[ $GROUP == js* ]]; then npm install -g casperjs; fi'
+    - 'if [[ $GROUP == js* ]]; then npm install -g casperjs@1.1.1; fi'
     - git clone --quiet --depth 1 https://github.com/minrk/travis-wheels travis-wheels
 install:
     - pip install -f travis-wheels/wheelhouse file://$PWD#egg=notebook[test]