Update menu.html

Add viewport meta tag in order to engage responsiveness on mobile devices. Below are screenshots of before and after on Motorola Droid 3 running Android 4.1.

Before

![2013-10-03 16 43 31](https://f.cloud.github.com/assets/1039832/1265786/d76369de-2c75-11e3-864a-4a5a1159f34b.png)

After

![2013-10-03 16 44 17](https://f.cloud.github.com/assets/1039832/1265788/de812012-2c75-11e3-8b2b-cd9d243e381f.png)
![2013-10-03 16 44 27](https://f.cloud.github.com/assets/1039832/1265790/dfe2ea44-2c75-11e3-97e2-4b2d7c3f86e0.png)