ignore compiled crate
don't make cargo-install the default
testing shenanigans
All types that satisfy Arbitrary must now be sendable.
Support recovery from task failures.

(rustc will do it for us, but quickcheck has to do it too so that
we can shrink appropriately.)

Sadly, it seems like this prevents stack closures from satisfying
the Testable trait.
clean rule
Forgot to remove this when trying to get stack closures working.
80 cols
Update for channel renaming.