Skipped tests and describes

[mackwic]

The famous xit and xdescribe !

When used, the runner print them as success, count them as skipped, and doesn't run them.

It needs a little change in design to tell the runner to skip them.

Note1: if #6 or #5 are implemented, the aliases also needs their focused counterpart.
Note2: could be nice to do it via the test name. It could also be a poor way to solve the problem without design change.

[regexident]

We already have 3 × 3 functions for creating suites/contexts/examples.

Any further addition of skipping variants (9 more functions each!) would be a bad idea, imho.

Instead we should consider adding support for tagging one's suites/contexts/examples, with which in place one could realize skipping by simply negatively filtering for a given tag.

The same applies to Focused tests and describes.