Remove unused Cucumber features

I forgot them in #104 :/
Remove dummy app dependencies

I also forgot them in #104.
Update Inch

Move to optimistic version requirement
Fix `header_names` option misbehaviour

The default header fields for both the token and the identifier
were omitted, when custom header names were present, even if
only one header name was customized.

Fixes #120
Merge branch 'fix-header-names-option-all-or-nothing-misbehaviour'