Double check that generate_toc.py is getting copied properly

[choldgraf]

In #208 it seemed that generate_toc.py wasn't being properly copied over. We should double check that it's copied properly and fix it if not.

[thammegowda]

I confirm it's not getting copied (tested on OSX)
generate_toc.py is not found in pip bundle

[thammegowda]

$ python -c 'from setuptools import find_packages; print(find_packages())'
['jupyter_book', 'jupyter_book.commands']

So, now we know why it happened: find_packages isnt including scripts dir

and now we know how to fix it:

$ touch jupyter_book/scripts/__init__.py
$ python -c 'from setuptools import find_packages; print(find_packages())'
['jupyter_book', 'jupyter_book.scripts', 'jupyter_book.commands']