Some tweaks for iOS devices

Hi there,

I just noticed and hopefully fixed few issues when I installed 2048 on my wife's iPhone (our whole family is now addicted to your game).

* Adds a launcher icon if you bookmark to your homescreen:

<img src="https://f.cloud.github.com/assets/121322/2394123/43088442-a9aa-11e3-8c38-962af205e5bf.png" width="50%">

* Hides the address bar when you launch from your homescreen:

|Before|After|
|---|---|
|![image](https://f.cloud.github.com/assets/121322/2394135/b036806e-a9aa-11e3-8f13-972ca8a762a3.png)|![image](https://f.cloud.github.com/assets/121322/2394128/8560d5f6-a9aa-11e3-8086-c3dd515ff73e.png)|

Submitted for your consideration.

Cheers,
 Lee :beers: