Make stars smaller on large screens, bigger on small screens

This makes it so that even devices like the iPhone 4 can tap the star ratings.

Various device resolutions appended:

![screen shot 2014-03-14 at 2 15 43 pm](https://f.cloud.github.com/assets/537700/2425974/ffd5cff2-abbd-11e3-9684-f6d525148d77.png)
![screen shot 2014-03-14 at 2 15 22 pm](https://f.cloud.github.com/assets/537700/2425975/ffd8dd78-abbd-11e3-90f4-4b0bb0e07ddf.png)
![screen shot 2014-03-14 at 2 15 33 pm](https://f.cloud.github.com/assets/537700/2425976/ffd95118-abbd-11e3-9387-328d41d91de5.png)
![screen shot 2014-03-14 at 2 16 16 pm](https://f.cloud.github.com/assets/537700/2425977/0006547e-abbe-11e3-8a04-ca689699f988.png)