I think this is worth a try. If it becomes a problem we can always
revert it. My rationale:

  - This is a good project for newbies to hack on. Nobody's respirator
    has bugwarrior as a dependency. If they break bugwarrior but the
    tests still pass, that's a good opportunity to write more tests.
  - The people who read the contributing docs are going to be better
    contributors than those who don't. Therefore, this is the place we
    want to encourage them to the maximum. I don't *think* it will
    encourage low-effort PR's.
  - When someone's struggling it is probably be easier to review their
    unfinished work early and intervene than to review a monsterous
    changeset they've cludged into working.

I'm assuming a symlink will work here.