var author = new Vue({
  el: '#author',
  data: {
    tab: "books"
  },
  methods: {
    showBooks: function() {
      this.tab = "books";
    },
    showAuthors: function() {
      this.tab = "authors";
    },
    showSeries: function() {
      this.tab = "series";
    }
  }
})