Add JS examples to Getting Started

This adds Javascript examples to "Getting Started" that work in Node.js and in the browser.

![image](https://cloud.githubusercontent.com/assets/555859/4392795/fe9088e8-4411-11e4-9729-c2fa7657c33e.png)
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![image](https://cloud.githubusercontent.com/assets/555859/4392798/0361ba9a-4412-11e4-84af-7536ebdfef53.png)