Fixes issue #247

This is a test and simple fix for issue #247 which causes filename not to be displayed on parse error.

The old output looked like:

```
arse error at :49. Found examples when expecting one of: comment, doc_string, row, scenario, scenario_outline, step, tag. (Current state: step). (Gherkin::Parser::ParseError)
```

The new output looks like:

```
Parse error at /Users/loberhub/projects/business_rules/features/entities/policy.feature:49. Found examples when expecting one of: comment, doc_string, row, scenario, scenario_outline, step, tag. (Current state: step). (Gherkin::Parser::ParseError)
```