worker source on Goutte's fork, see https://github.com/Dreckr/Worker/issues/12
this is a test, should be reverted later on.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	pubspec.yaml
Extracted gherkin parsing logic from task, so that we may use it without Isolates.
Custom Worker fork with no dep to dart:io
Made sure feature can still be executed without worker.
Fix for empty optional runTags
BADASS refacto -- Will be painful to merge in case of conflicts:
- Statuses as output
- Buffer choice now left to the runner. Using ColoredFragmentsBuffer internally.
- missing step defs logic moved out of buffer
Merge pull request #16 from Goutte/master

Another step towards Dartium support