readme: consistent screenshot sizes

Author: ebidel

README.md

@@ -8,31 +8,35 @@ Output from some of the examples:
 
 Test lazy loading strategy by seeing CSS/JS code coverage usage across page load.
 
-<img width="741" alt="screen shot 2018-02-26 at 10 20 41 am" src="https://user-images.githubusercontent.com/238208/36687690-2de2bbaa-1adf-11e8-912b-e21cda0160ce.png">
+<img width="500" alt="screen shot 2018-02-26 at 10 20 41 am" src="https://user-images.githubusercontent.com/238208/36687690-2de2bbaa-1adf-11e8-912b-e21cda0160ce.png">
 
 ### [verify_sw_caching.js](./verify_sw_caching.js)
 
 Verify all the resources you expect are being cached by a service worker for offline.
 
-<img width="623" alt="screen shot 2018-03-01 at 5 09 32 pm" src="https://user-images.githubusercontent.com/238208/36878494-1b4098d6-1d74-11e8-93d2-492e3b2f1877.png">
+<img width="500" alt="screen shot 2018-03-01 at 5 09 32 pm" src="https://user-images.githubusercontent.com/238208/36878494-1b4098d6-1d74-11e8-93d2-492e3b2f1877.png">
 
 ### [google_search_features.js](./google_search_features.js)
 
 Gut check your page to make sure it renders correctly for Google Search.
 
-<img width="747" alt="screen shot 2018-03-07 at 12 50 32 pm" src="https://user-images.githubusercontent.com/238208/37125450-804ad8c0-2221-11e8-8c96-7c5af582778f.png">
+<img width="500" alt="screen shot 2018-03-07 at 12 50 32 pm" src="https://user-images.githubusercontent.com/238208/37125450-804ad8c0-2221-11e8-8c96-7c5af582778f.png">
 
 ### [speech.js](./speech.js)
 
 Make your browser talk.
 
-[![Speech demo is action](http://img.youtube.com/vi/v5ZXRgzR7Wc/0.jpg)](https://www.youtube.com/watch?v=v5ZXRgzR7Wc)
+<a href="https://www.youtube.com/watch?v=v5ZXRgzR7Wc" target="_blank">
+  <img width="500" alt="Speech demo in action" src="http://img.youtube.com/vi/v5ZXRgzR7Wc/0.jpg">
+</a>
 
 ### [pacman.js](./pacman.js)
 
 Play the Google Pac-Man Doodle.
 
-[![Playing Puppeteer Pacman](https://user-images.githubusercontent.com/238208/38574488-c45df5a0-3cad-11e8-90fe-001afc2d4625.png)](https://youtu.be/5CihR6Z9sX8)
+<a href="https://youtu.be/5CihR6Z9sX8" target="_blank" title="">
+  <img width="500" alt="ePlaying Puppeteer Pacman" src="https://user-images.githubusercontent.com/238208/38574488-c45df5a0-3cad-11e8-90fe-001afc2d4625.png">
+</a>
 
 ### [element-to-pdf.js](./element-to-pdf.js)