code: function(tag) {
      var posts = [];
      for (var key in this.posts) {
        if (this.posts[key].tags && this.posts[key].tags.indexOf(tag) !== -1) {
          posts.push(this.posts[key]);
        }
      }
      return posts;
    }
docs: Get a set of posts for a tag.
  
  @param {String} Tag name
  @return {Array}