A better test scaffolding, fixed stderr the "Inherit" way

Hello Greg,

the test process we had before was clumsy. I've created a new test machinery based on some experience I've gained working with the Snap team. Now we have a separate cabal project were all our tests will live. Look inside `TestMain.hs` for a beautiful example of how we can execute our specs easily.

Furthermore, now we have a single shell script, `testall`, which will run the main file AND call hpc on Shelly; yes, we now have test coverage!

I've fixed the stderr the "Inherit" way, and tests seems to confirm that my patch is indeed correct; I had a failing test in FailureSpec.hs, applies my fix, green lights all the way down :)

Hope you like this new exciting stuff!
So, to run the whole test suite:

``
cd test
cabal install && ./testall
``

Enjoy!