Document AfterFeatures event (close #171)

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 in #120 to get these tests to run correctly.

Conflicts:
	bin/cucumber.js
	features/cli.feature
	features/step_definitions/cli_steps.js