Automatically expand scope of example groups

Given a subject Foo::Bar#baz mutant will run example groups with
description starting with:

  - Foo::Bar#baz
  - Foo::Bar
  - Foo

This basically means you can kill a mutation via a dedicated spec for a
given method, all specs for a given object or all the specs within the
object's namespace.

In most of the cases you should target killing mutations via a dedicated
spec for a particular method *however* there are valid cases where
implicit coverage is absolutely fine.