Multistep definitions and randomization of scenario execution order

2017-04-29

• added support for nested steps. From now on, it is possible to return
  godog.Steps instead of an error in the step definition func.
  This change introduced few minor changes in Formatter interface. Be
  sure to adapt the changes if you have custom formatters.

2017-04-27

• added an option to randomize scenario execution order, so we could
  ensure that scenarios do not depend on global state.
• godog was manually sorting feature files by name. Now it just runs them
  in given order, you may sort them anyway you like. For example godog $(find . -name '*.feature' | sort)