Clean up acceptance tes
Clean up acceptance tes

Notes:

1. We need to use @spawn here because the puts statements are sent directly
   to STDOUT rather than being sent to the io stream passed into
   `Cli::Main`.
2. `expect` doesn't work in the event block - it's evaluated in the
   context of nil. Would something else make more sense? I'm not sure.

cc @tooky

phoebeclarke/cucumber-ruby,shadow000902/cucumber-ruby,phoebeclarke/cucumber-ruby,enkessler/cucumber-ruby,danascheider/cucumber-ruby,twalpole/cucumber,cucumber/cucumber-ruby,danascheider/cucumber-ruby,enkessler/cucumber-ruby,cucumber/cucumber-ruby,shadow000902/cucumber-ruby,enkessler/cucumber-ruby,marxarelli/cucumber,twalpole/cucumber,richarda/cucumber,cucumber/cucumber-ruby,richarda/cucumber,marxarelli/cucumber