code: function init (update) {
        var self = this
        var head = (typeof self.$options.head === 'function') ? self.$options.head.bind(self)() : self.$options.head
        if (!head) return
        Object.keys(head).map(function (key) {
          var prop = head[key]
          if (!prop) return
          var obj = (typeof prop === 'function') ? head[key].bind(self)() : head[key]
          if (key === 'title') {
            util[key](obj)
            return
          }
          util.handle(obj, key, 'head', update)
        })
        self.$emit('okHead')
      }
docs: Initializes and updates the elements in the head
  @param  {Boolean} update