Fix README.md markup

Before:
![2014-06-30 1 21 24](https://cloud.githubusercontent.com/assets/290782/3423765/72e7c1be-ffa9-11e3-9268-ef83fa1a739e.png)

After:
![2014-06-30 1 20 36](https://cloud.githubusercontent.com/assets/290782/3423762/56ef7c7c-ffa9-11e3-949e-8719c25acbe8.png)