Remove notes/ folder. This stuff is in nbdiff-docs.
Remove prototype. This stuff is in the main program now.
Removing docs/ folder. This is in nbdiff-docs
Add install_requires to setup.py.

So people don't have to run pip install -r requirements any more.
Merge pull request #136 from tarmstrong/add-install-requires

Add install_requires to setup.py.
Change open_browser() to use threading instead of multiprocessing.
Merge branch 'master' of https://github.com/tarmstrong/nbdiff into newlinediff
added some tests
test_diff_lines2 is failing :(