RuleSet is now an interface, and Conway has placeholder code.
Merge branch 'master' of github.com:earwig/goldfish
Implement Conway, add states variable to ruleset.
Merge branch 'master' of github.com:earwig/goldfish
Merge branch 'master' of github.com:earwig/goldfish
Fixed awful typos in Patch, constructors in grid

    Also switched back to a class for RuleSet.
    Because intefaces and static methods don't mix.