add cleanup crew

[nikomatsakis]

First draft of describing the "cleanup crew" ICE-breakers team.

[nikomatsakis]

OK, I pushed some basic advice about cargo-bisect-rustc. I'd like to push some advice about finding the set of PRs in a nightly, but I'm actually not sure the best way to do that.

[pnkfelix]

OK, I pushed some basic advice about cargo-bisect-rustc. I'd like to push some advice about finding the set of PRs in a nightly, but I'm actually not sure the best way to do that.

The biggest problem here is that if you want to do something like git log --author=bors --format=oneline COMMIT1..COMMIT2, you need a local checkout, right? Because I would agree with that, and is a further argument for investing effort in resolving rust-lang/cargo-bisect-rustc#40

(I'm not sure if you find the above git log invocation awkward; it seems pretty stream-lined to me.)

[nikomatsakis]

Yes, the biggest problem is probably needing a local checkout -- but I also think we could get more streadmlined. My ideal would be something that extracts and prints markdown with a list of PR numbers

* "blah blah blah", PR #123 by @so-and-so

[spastorino]

@nikomatsakis this is great, left a comment about the last section.

[spastorino]

Looks good to me now, maybe as @lqd mentioned in one case, we could provide links for all the streams that show up there.