[buddy/hashers] Fix reflection warnings.

[harold]

Thanks for this excellent library, we use it to hash many many strings, and it works great.

Similar to this buddy-core pull request: https://github.com/funcool/buddy-core/pull/53

• but for this buddy-hashers repo

Fixes https://github.com/funcool/buddy-hashers/issues/20

[harold]

Following up on this: https://github.com/funcool/buddy-core/pull/53#issuecomment-737811710

I've merged master into this branch, fixed the conflicts, and lein check and lein test are both clean.

Hope that helps.

[mjosefs]

This looks a bit idle – @niwinz any chance of getting it merged? I'd be happy to provide amendments if needed.