Moved table mapping to new feature structure
Migrated unicode table to new feature structure

Note that `@spawn` unfortunately became necessary here to prevent the
error discussed on #458.
Moved regression feature as scenario in new structure
Move several scenarios to new homes
Remove scenario that's tested elsewhere
Extract `-r` scenario into new feature
Extract @-notation to new home in new features
Made steps more like those in rerun_formatter

We are trying to standardise on one set of example steps within the
whole codebase, to clean up the docs.
Moved language help to new features

Took the opportunity to make the preamble clearer.
Moved --expand outlines option to new features
Added @spawn to fix build failure
Remove tab indentation regression feature

The commit which fixes the original bug is 3897989. The equivalent file
now is `doc_string.rb` which no longer appears to contain indentation
stripping code, so I can't see a way to break it outside of Gherkin.
Move debug formatter to new home
Move lighthouse bug 475 regression to unit test
Simplified + clarified examples in feature
Merge pull request #459 from chrismdp/migrate-unicode-table

Migrated unicode table to new feature structure
Merge pull request #463 from chrismdp/migrate-expand-outlines

Moved --expand outlines option to new feature structure
Merge pull request #465 from chrismdp/migrate-table-mapping

Moved table mapping to new feature structure
Merge pull request #468 from chrismdp/migrate-bug-475

Move lighthouse bug 475 regression to unit test
Merge pull request #466 from chrismdp/migrate-bug-464-feature

Moved regression feature as scenario in new structure