Readme.md: Improve layout of `Team` section

Before:
![before](https://f.cloud.github.com/assets/1223565/433207/7101cd74-aec2-11e2-8271-343438f2881f.png)

After:
![after](https://f.cloud.github.com/assets/1223565/433215/baf28fea-aec2-11e2-9fb0-50fcd51c3179.png)