node status added to readme

What this project needs is more badges!

Helps us see at-a-glance what the latest version on npmjs.com is, and also provides a handy link to the project on npmjs.com.

![screen shot 2014-12-19 at 14 43 48](https://cloud.githubusercontent.com/assets/5111927/5505946/778ba336-878d-11e4-9e35-c003a44e3cd6.png)