Chapter Prose

First draft of the chapter prose, in rst form for now. I'm requesting PR to have someone look at the prose. I've also included an svg diagram, but you'll have to pull the repository to see it. I don't think it's viewable within github...

If you want to pull this, this is the 'chapter' branch from https://github.com/malini/500lines
This section feels like filler in that it does not explain much of the project beyond listing the files contained within it. I think more explanation is necessary on the subject of inter-process communication beyond:

> Each of these three processes communicate with each other using sockets, and since the code used to transmit information is shared by all of them, there is a helpers.py file that contains it, so each process imports the 'communicate' function from here instead of having it duplicated in the file.