Refresh a lot of the copy

This includes some small and some larger(er) changes, which I'll call out specifically in a moment, but generally:

* Typos and wording (small)
* Bring some tech stuff up to date (small)
* Change a few things about the rails engineering job description (bigger)
Open to a better wording here.  Idea is to emphasize that we do do code reviews, but they are not dreaded experiences but purposeful and helpful.