Remove Dynamic Search Methods?

As brought up in #15, messing with `method_missing` can be hairy and have unexpected and hard-to-debug consequences. The feature that we're using `method_missing` to support is the dynamic search methods (like `Game.search_by_title("fighter")`). Personally, I've never used this feature. And I feel like these *kinds* of features are falling out of favor in the community in general.

Do you use this feature? Would you be sad to see it go? I'd love to hear from both other maintainers as well as users.

Obviously, this would require a major version bump to release, so I'm thinking we'd add a deprecation warning to some patch release and then rev to 4.0 before ripping it out, if that's the path we decide one.