Implement finishResumable*
Compile tests with -O0
Add ResumableConduit tests

I did a couple "clumsy" things:

 * Import Data.Conduit etc. unqualified

 * Use partial do patterns instead of shouldBe

I know this is inconsistent with the existing code, but I left it this way
for a philosophical reason: writing tests should first and foremost
be easy.  It's better to have some tests that produce ugly failure output
than it is to not have those tests at all.  If a test fails later and we
want to know what the failure output was, we can replace partial patterns
with `shouldBe` as part of the troubleshooting process.
Use embedFinalizer so resumeConduit does not have to act like pipeL on end
Clean up resumeConduit so it's easier to compare with pipeL
Test resumable source finalization