def register_plugin(type, klass)
      type = type.to_s
      @plugins[type] ||= []
      @plugins[type].push(klass) unless @plugins[type].include?(klass)
    end
def register_plugin(type, klass)
      type = type.to_s
      @plugins[type] ||= []
      @plugins[type].push(klass) unless @plugins[type].include?(klass)
    end
Register a new plugin, can be used to load custom plugins

 @param type [String] type for the klass
 @param klass [Class] klass of the plugin to add