capture Debug.log and present it with a failing test

When I'm trying to figure out why a test is failing, I'll often put `Debug.log` statements into the things I'm modifying to see what's up. If I run my whole test suite after that, I get way more log messages than I want, with no indication of which ones are actually relevant to the test failure I'm trying to debug.

I'd really like it if, instead, elm-test would capture stdout and associate it with a given test run. A few other test frameworks I've used (py.test maybe? but it's been a while) do this and it's super nice.

If I could have a pony, I'd also like this for fuzz tests. I'd like to only see the debug messages from the final shrunk failure case!