def new(params = {})
      attributes = params.merge(default_params)
      instance   = member_class.new(attributes)

      new_member(instance) do |member|
        self << member
      end
    end
def new(params = {})
      attributes = params.merge(default_params)
      instance   = member_class.new(attributes)

      new_member(instance) do |member|
        self << member
      end
    end
Initializes new {member_class} with `params`

 - Ensures a parent id is merged into `params` (see #default_params).
 - Defines method `#save` on new collection member
 - Adds new item to collection

 @example usage

   >> person = BlockScore::Person.retrieve('55de4af7643735000300000f')
   >> person.question_sets.new
   => #<BlockScore::QuestionSet:0x3fc67902f1b4 JSON:{
     "person_id": "55de4af7643735000300000f"
   }>

 @param params [Hash] initial params for member

 @return instance of {member_class}

 @api public