Split this into two methods?

It would be nice if this method either returned the policy class checked, or if there was some way to determine this without re-implementing the policy lookup logic.

https://github.com/varvet/pundit/blob/56af8f3ce25bf1eea47ec877f840b3de6fb32cdc/lib/pundit.rb#L76

One way would be to split this into two methods:

• Map incoming arguments to a policy.
• Raise an exception if the policy isn't satisified.

Would you accept a PR for this?