Fix gravatar image size

Before:
![2013-05-12 20 29 46](https://f.cloud.github.com/assets/290782/492841/4e89c03a-baf7-11e2-936c-f5141e60eb3c.png)

After:
![2013-05-13 2 15 15](https://f.cloud.github.com/assets/290782/493197/891dec5a-bb27-11e2-8398-95c408621c71.png)