Improve code by using context managers to handle closing of files.
Also, replace the flame-war indexing comment for one with some explanations to why things are as they are.
IPython still exists, but the notebooks have been spun off into their own project called Jupyter. This file change:
* updates the pip install queue so that Jupyter gets installed
* removes the vague "get set up with IPython" (pip will install IPython with Jupyter), and
* replaced the suggestion to work in "the IPython notebook" with "a Jupyter notebook".
