Report is not written before the end of the tests execution

So you can't see report while tests are running. And if you abort execution you also can't see report.
This issue is caused because report is writing only in the end. [Link on commit](https://github.com/simondean/parallel-cucumber-js/commit/c113a5725bd6d5127d63fafffc192dbce2c977c5#diff-0db7922df91b6129dc41122748789eb1R34)