Allow show only the errors in the report.

[sarvaje]

When we are validating a lot of files, it can be difficult to find the errors.

[chmac]

This was a show stopper for me also, so I hacked a quick & dirty solution by modifying the code. You can see it in my fork on the omit-success-output branch.

https://github.com/chmac/markdown-link-validator/tree/omit-success-output

[mi-hol]

I'd suggest new options

-ov containing file names of all valid .md input files

-oi containing file names of all invalid .md input files