Should before and after run with skip?

ava: 0.18.2

```js
import test from 'ava'

test.before(() => {
  throw new Error('should not run?')
})
test.after(() => {
  throw new Error('should not run?')
})

test.skip('some skipped test', t => { })
```

Currently the `before()` and `after()` is run even if the file contain only skipped tests.
Is that the expected behavior?