re-add instance matching with a proper 'instance' property
Update README with instance matching
Refactor some of pull request #27 improvments

* Restore the old README column width to avoid issues with some markdown
implementations

* Rename class_client and instance_client to c_rules as the old name isn't
  significative anymore.

* Merge copy/pasted code back into a single block

* Remove the unused `low`, `rules_c` and`rules_i` temporary variables
Fix readme (tabs accidently introduced by pull #27)