Remove 'kind' instance method because it is shadowed.
Remove 'kind' instance method because it is shadowed.

Details:
* Our ActiveSupport class_attribute declaration for:kind
  creates accessors for both the class and instances.
  Instances will default to the class value, but may have its own
  set instance values... this is a bit dangerous if we're
  creating new Serf Messages by merging attributes of others.
  (#to_hash vs #attributes) in Serf Messages.

byu/serf