Merge pull request #1 from david-martin/screenshot_on_failure

Screenshot on failure
Initial poc for test workers
Allow auto detect number of workers
Remove logs
Remove console
PR tidyup
Merge pull request #2 from david-martin/test-workers

Test workers
Disable concurrency if filtering flag passed
Only include js files for test concurrency
Merge pull request #3 from david-martin/filter-non-js-files-from-concurrency

Only include js files for test concurrency
Pause while taking screenshot