Trigger smartanswerOutcome at result step

The 'smartanswerAnswer' event incorrectly replaced 'smartanswerOutcome' in this commit:

https://github.com/alphagov/smart-answers/commit/18b773509702533e1ddc945b6dfe62da78a87679#L0L73

Now fixed and tested to ensure the code attached to 'smartanswerOutcome' in https://github.com/alphagov/static/blob/master/app/assets/javascripts/analytics/tracking.js works.