Use jupypter-pip to install notebook extension js automatically during setup.py

[jchuahtacc]

Automatically installs qgridjs to nbextensions using jupyter-pip. No need for separate nbinstall function call.

[TimShawver]

I get the following error when I try to run pip install -e . on your branch:

    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/Users/tshawver/repo/qgrid-master/setup.py", line 60, in <module>
        cmdclass=cmdclass('qgrid/qgridjs'),
      File "/usr/local/lib/python2.7/site-packages/jupyterpip/__init__.py", line 50, in cmdclass
        from IPython.html.nbextensions import install_nbextension
    ImportError: No module named IPython.html.nbextensions

Any idea on how to fix it? Seems like jupyter-pip is looking in the old location for the nbextensions module.