Amortized calculations

This calculates the loan comparison section using an amortization table. (Bonus: also fixes the browser issues for custom select drop downs).

![screen shot 2014-06-10 at 7 06 03 am](https://cloud.githubusercontent.com/assets/212533/3232214/f8a3d0ec-f0b1-11e3-8788-52493146da40.png)