Add fail-fast option

Also modify ruby-version to 2.0.0-p195
Start on actually use fail_fast
Fix a test
Implement break when fail_fast
Add one more test
Add the feature
Allow scenario level fail fast
Reformatting a little bit
Refactoring

DRY up FeatureGenerator
Address review comments

- Given -> And
- Align a string
Add some comments
Try a different patch level for travis
Patch 195 is not working on travis
Bump gem version; Edit CHANGELOG
Merge pull request #139 from ywen/feature/fail-test

Feature/fail test