Readme doc updates

A variety of updates to the README. Two main goals with these updates:

- Be consistent in formatting
- Be consistent in using RSpec 3 syntax
Github generates it for you. It's in the associated 9bdb0a31 commit message:

> Remove explicit anchor tags.
>
> Github READMEs not automatically add anchor links to the headers.

Looks like I have a typo in the commit message (>ლ)