Present test results as table

[gdalle]

Hack into @testset to retrieve?

[adrhill]

Outer testsets only return a parsable structure when they pass, so this requires a new testset type. However, custom testsets don't get printed when called inside of a DefaultTestset.

Leaving this open since a custom testset might also be required for #112.

[adrhill]

Closing for now as this would require either:

• defining custom testsets (see above for caveats)
• duplicating correctness.jl as it currently makes use of DefaultTestsets via @testset