#898 - Made Jetpack sign-in screen class less

#898 

Before and after:

![ios simulator screen shot dec 19 2013 10 22 23 am](https://f.cloud.github.com/assets/3904502/1784925/07da09dc-68db-11e3-85cf-399512b90e0b.png)
![img_7892](https://f.cloud.github.com/assets/3904502/1784926/07da2552-68db-11e3-8e54-b2a95f01e2bf.PNG)