Allow top-level Configure to return an error

[elezar]

No description provided.

[klihub]

LGTM.

[klihub]

For context: We discussed last week whether cache.Configure() should be changed to not return an error, since #187 got merged and it changed Option to not have the possibility to return errors. But we concluded that #187 might have been not such a good idea, as we might want to add an Option in the future which should be able to fail. At that point we'd need to flip cache.Configure() back to return an error, so we might as well omit that API-braking change now instead of revert it in the future. But the package-level/default cache Configure() should have the same signature as cache.Configure() (after all that's what it boils down to), and since the consensus now is that we don't remove error from the latter, the former should updated to reflect this, too.

[marquiz]

LGTM. Makes sense to me