fix code block, heading level, typo

There is a couple of things:

1. A few backtick'd text under Installation section don't seem right. In reST, inline literals uses double-backtick, mistake?
2. `-use-wheel` doesn't exist on my Linux with wheel package 0.22.0 and 0.23.0. Is that Windows-only or just an error?

If you they are indeed errors, and you need me to fix for you, just let me know, I will add another commit to this PR.