review of parts 1 and 2

Here are changes based on review of parts 1 and 2. Most are grammatical or are to improve awkward wording. I tried to keep the tone the same. I added very little actual content. Also, did some style review of the code. Mostly this is based on foodcritic/rubocop best practice but some is my own opinion and what I do in production code. Feel free to question any of it. I'll explain if needed.