Creating basic PyPI package layout.
Cleaning up setup.py and HISTORY
Merge pull request #39 from tarmstrong/create-pypi-package

Create pypi package
Add entry_points to python package.
Merge branch 'master' into branch-new-layout
Write script to use single cell .html files to build diff prototype
Add example of deleted cell to nbdiff prototype
Add staging checkboxes to nbdiff prototype