Documentation and test for AfterFeatures event

I spent ages doing the wrong setup for AfterFeatures to try and close my browser at the end of the tests, so I thought that including a test and better documentation might help other people.

This also fixes the unimplemented cli.feature step, and failing assert due to console coloring.

I had to apply the [patch from comments](https://github.com/cucumber/cucumber-js/issues/120#issuecomment-22955066) in #120 to get these tests to run correctly.