Notes on testing for early return.
Use returned array as subsequent step arguments.

Now when an array is returned using `return` the elements of the array
are used as the arguments to the subsequent step. If you want to return
multiple values to be passed as multiple arguments to the subsequent
step, return them as an array.

So, now if you want actually want to return an array to be used as the
sole argument to the subsequent step, you need to put that array in an
array to be explicit. When in doubt, wrap it up in an array.

Closes #188.