Fix for a minor but annoying unicode error

To find this bug I managed to behave-parallel to run without having parallel_element variable in the Configuration object set. The error I got was the misleading

UnicodeEncodeError: 'ascii' codec can't encode character u'\u2019' in position 17: ordinal not in range(128)

instead of the helpful

ValueError: execute_steps() called outside of feature

So here is my fix. Such as it is.