Remove callbacks in examples.

There's no need to put a function in a callback if we're doing absolutely nothing else with either callbacks.

README.md

@@ -26,10 +26,10 @@ window.onload = function() {
     });
 
     // (example) update the size and positioning on window resize
-    window.onresize = function() { contain.update(); };
+    window.onresize = contain.update;
 
     // (example) update the size and positioning on orientation change
-    screen.addEventListener('orientationchange', function() { contain.update(); });
+    screen.addEventListener('orientationchange', contain.update);
 };
 ```