Lessons grammar and style validation

[s-matyukevich]

I am not a native English speaker. I did my best to verify the lessons, though they still can contain a lot of grammar mistakes. If you want to help the project, you can just select any lesson or chapter and submit a PR with the changes.

[gmcclins]

I am not so hot with grammar, but I am currently rephrasing some things to either make more clear or just flow nicer. I will fix what grammar jumps out at me.

[s-matyukevich]

Thanks, @gmcclins!

[amo7een]

I'm a new technical writer, with a good understanding of grammar. I can also take a look.