Sketch out first 3 sections

These sections were originally IPython notebooks that I converted to markdown. This is missing a lot of explanatory text, but that will come later. I'm really not sure whether this is the right process for version control. I suspect, that each build will create new images, but I guess the text diffs are manageable (compared to diffs of ipynb files) so that's a definite plus.

Note that I created a separate file for plot helpers. I don't like having notebooks cluttered with code that isn't relevant to the topic. I plan on discussing the helpers, but just having them in a separate file minimizes distraction.
Hahaha, I actually thought long and hard about this :) I think something similar came up during the paper. I think "segmentation" is jargon, whereas "segmenting" is not. That said, the meaning probably isn't immediately clear to most people. I'll make the change.