Allow both 'a' and 'the' in step, as documented

[mvz]

Summary

Allow both 'a' and 'the' in file mode checking step, as documented in the corresponding feature file.

Details

Updates the step regexp to allow both 'a' and 'the' at the start. So, now 'a file named ...' is properly matched.

Motivation and Context

Oddly, on JRuby 9.2.7.0, cucumber fails on undefined steps. This made the feature for this step fail and surfaced the problem.

How Has This Been Tested?

Nothing yet. We need to have some way to detect undefined steps better.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (cleanup of codebase without changing any existing functionality)
• Update documentation

Checklist:

• I've added tests for my code
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[luke-hill]

Seems legit