Opt-in to output 'Skip as no hooks defined'

Hi,

I find it useful not to print out mocked test when skipped.
So in `test-runner.coffee`:

```
# No Hooks for this test
if not hooks.hasName(test.name) and options['hooks-only']
# suite.addTest new Mocha.Test 'Skip as no hooks defined'
return
```

Read test-runner.coffee at the hooks-only check and trace how options are supplied. Make the 'Skip as no hooks defined' output optional while preserving the existing return behavior for tests without hooks; done means the message appears only when the new opt-in is enabled.

Written by the indexing model from the issue text.