[Catalyst] Organize tests in sub-directories

[Octavian Râşniţă]

Hello,

I would like to structure the t directory as lib/MyApp is structured. Is it 
possible to be able to configure the app somehow so `make test` checks all 
the test files even if they are in sub-directories?

`prove -r -l t` can do this, but it works well only under Linux or if I also 
add the -j parameter and a big enough number of parallel jobs, so I'm not 
sure it will always work.

Thanks.

Octavian