code: function freeze (freeze) {
      if (defined(freeze)) {
          // set default
          immutable.defaultFreeze = freeze ? true : false
          // return immutable
          return ImmutableCore
      }
      // return default value
      return immutable.defaultFreeze
  }
docs: @function freeze
  
  get/set the default freeze option
  
  @param {boolean} freeze
  
  @returns {ImmutableCore|boolean}