install local mathjax on travis (2.x)

weird CDN things are happening on Travis

.travis.yml

@@ -1,18 +1,19 b''
 # http://travis-ci.org/#!/ipython/ipython
 language: python
 python:
     - 2.7
     - 3.3
 before_install:
     # workaround for https://github.com/travis-ci/travis-cookbooks/issues/155
     - sudo rm -rf /dev/shm && sudo ln -s /run/shm /dev/shm
     - easy_install -q pyzmq
     - pip install jinja2 sphinx pygments 'tornado<4' requests mock
     # Pierre Carrier's PPA for PhantomJS and CasperJS
     - sudo add-apt-repository -y ppa:pcarrier/ppa
     - sudo apt-get update
     - sudo apt-get install pandoc casperjs nodejs
+    - python -m IPython.external.mathjax
 install:
     - python setup.py install -q 
 script:
     - cd /tmp && iptest