Add Perl6's YAMLish to the matrix

[Leont]

It's already supported in yam-editor, but not yet in the Matrix. At the recent Perl Toolchain Summit I fixed an important bug that I think previously prevented its inclusion.

[perlpunk]

@Leont thanks. My reason for skipping it was that it was too slow on the machine I moved to. I set a timeout for each test at 3 seconds. The plan was to check if a new rakudo build would improve performance. Still haven't had time though...

[Leont]

It should precompile, so that shouldn't be an issue anymore. It certainly was in the past though.

[perlpunk]

yeah, I've seen that in the past, that only the first call of the script is slow, but at some point it started to be slow for every call.

[perlpunk]

rakudo 2017.04 seems to be faster, i'm working on including yamlish...