updates to travis testing: - run coveralls, codecov on js environment as well as python - only test OS X y27 & y34 to save time.
updates to travis testing:
- run coveralls, codecov on js environment as well as python
- only test OS X y27 & y34 to save time.

original-commit-id: 3b84ca296ec2c5e42440e5e566f41fc544da9771
original-commit-url: https://github.com/ipython-contrib/IPython-notebook-extensions/commit/3b84ca296ec2c5e42440e5e566f41fc544da9771

jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator