Turn cpangrep-matcher into an object, similar to cpangrep-indexer

I really only wanted to add an option to use a non-default slab dir, but
got carried away. The functionality is the same, and this has been
tested and found working on the new cpangrep KVM I'm building.
Merge pull request #34 from seveas/matcher-object

Turn cpangrep-matcher into an object, similar to cpangrep-indexer