Custom formatter for Cucumber that defends against timecop overriding Time.now.

The _circleci_formatter.rb file should be dumped into the features/support directory and specified with Cucumber's --format flag:

bundle exec cucumber --format CircleCICucumberFormatter::CircleCIJson

Timecop redefines Time.now to Time.now_without_mock_time. If that method exists, then we call that method instead of Time.now.

This approach is somewhat brittle because it relies on the internals of before_step and after_step not changing.