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)
One of several changes trying to include the notion that we as a team don't know everything and aren't granting wisdom down to candidates.  Rather that stuff we don't know is an important thing a candidate can bring.