Bucket-typed buckets access properties of untyped bucket [JIRA: CLIENTS-61]

We can remove the `maybe_encode` functionality altogether. It checks to see if we're in an encoding-aware Ruby, and forces the given string into BINARY encoding if we are. This is now done inside Beefcake: https://github.com/protobuf-ruby/beefcake/blob/master/lib/beefcake/buffer/encode.rb#L107