code: function filterPrompts( PromptAnswers, generator_prompts ) {
    return filter(
      generator_prompts,
      function iteratee( prompt ) {
        return typeof PromptAnswers.get( prompt.name ) === 'undefined';
      }
    );
  }
docs: if a prompt.name already exists in PromptAnswers.answers that prompt will not be returned in
  the resulting Array
  
  @param {PromptAnswers} PromptAnswers
  @param {Array} generator_prompts
  @returns {Array}