Get the related categories for a category
@param opts [Hash] options hash of parameters @option opts [Integer] api_key 32 character alpha-numeric lowercase string @option opts [String] file_type A key or file extension that indicates the type of file to send @option opts [Integer] category_id The id for a category @option opts [String] realtime_start The start of the real-time period @option opts [String] realtime_end The end of the real-time period @return [Hashie::Mash] Hash containing the results