text: self.addEventListener('install', function(event) {
      event.waitUntil(
        caches.open('static-cache-v1')
        .then(function(cache) {
          return cache.addAll([
            '.',
            'index.html',
            'css/main.css',
            'https://fonts.googleapis.com/css?family=Roboto:300,400,500,700',
            'images/still_life-1600_large_2x.jpg',
            'images/still_life-800_large_1x.jpg',
            'images/still_life_medium.jpg',
            'images/still_life_small.jpg'
          ]);
        })
      );
    });
    
    self.addEventListener('fetch', function(event) {
      event.respondWith(caches.match(event.request)
      .then(function(response) {
          if (response) {
            return response;
          }
          return fetch(event.request);
        })
      );
    });