def register_data_path(path)
      path = File.expand_path(path)

      DataPaths.register(path)

      data_paths << path unless data_paths.include?(path)
      return path
    end
def register_data_path(path)
      path = File.expand_path(path)

      DataPaths.register(path)

      data_paths << path unless data_paths.include?(path)
      return path
    end
Registers a path as a data directory.

 @param [String] path
   The path to add to {DataPaths.paths}.

 @return [String]
   The fully qualified form of the specified path.

 @example
   register_data_dir File.join(File.dirname(__FILE__),'..','..','..','data')

 @raise [RuntimeError]
   The specified path is not a directory.

 @since 0.3.0