Follow the convention of using `::` for describing class methods
Simplify file sample used for some tests
Stop sorting paths
Use RubyCritic's version as a cache key in the name of the revision file

Basically without this change, updating to a new version of the gem
would sometimes cause things to blow up since in the Serializer we're
loading old code with `Marshal.load`. This a terrible way to keep
snapshots, we should probably use a DB like SQLite3.