Grammar fixes and word swaps

Ran through Foundations and Intermediate and found some words that could be modified. I can revert some of these commits if need be.

I went through advanced, and there's a lot of content there. Didn't notice anything at first pass though
> A well-named `diff` option switch allows

Since this line is already getting edited, how about we lose the "well-named" wording? Sounds odd to me :ear:s.