Making sure setSize is a function

At work I was observing some really random `Object #<HTMLEmbedElement> has no method 'setSize'` errors.

It wasn't obvious what the problem was. My conclusion was that these people might be blocking it on purpose somehow. So I added some code to zeroclipboard to handle things more gracefully when they fail.

```js
if (flashState.ready === true && flashState.bridge && typeof flashState.bridge.setSize === 'function') {
  flashState.bridge.setSize(width, height);
}
else {
  flashState.ready = false;
}
```

What I'm doing differently, first I added a check so that if `typeof flashState.bridge.setSize` is not `'function'`, don't try and use the `setSize` method.

Also if the logic is false for any reason, then I set the `flashState.ready` to false. Just to avoid any other weird things later on.

@JamesMGreene