Allow passing a reason for skip

[cardil]

Skipping test is useful, but that should be pairs with proper reporting. Knowing why a given test was skipped, having only logs, is a must in many organizations.

I propose to expand the API to allow passing a reason, why a given test is being skipped. That reason should be reported to all registered test reporters for further processing.

[matosjoa]

I would love to see this in place too ;)