Set overflow-y to auto

Before:
![app-settings-scroll](https://f.cloud.github.com/assets/533222/2451086/699c7e2a-aec2-11e3-8859-381bdb475de5.png)

After:
![app-settings-scroll1](https://f.cloud.github.com/assets/533222/2451092/71808596-aec2-11e3-9613-35d2268f3225.png)
![app-settings-scroll2](https://f.cloud.github.com/assets/533222/2451093/71a537a6-aec2-11e3-80f0-99dd24dcdfdb.png)
@jancborchardt @MorrisJobke