A bunch of very simple edits to make the fundamentals page more readable

[jpnance]

In this commit, I'm only editing the fundamentals page but I imagine this is the most-read page within the project, so I'm hoping it makes the biggest impact. By and large, I'm just adding commas to better convey tone. My hope is that none of these changes are at all worth arguing about.

[istudyatuni]

Maybe it's incorrect, when you change 3d to 3D in links here