fix(rxForm): style before of selects to allow for border

![pr for ants](https://cloud.githubusercontent.com/assets/1529366/5343710/1cfc1c10-7ece-11e4-9d38-88cf52cbf574.jpg)

## Before
![screen shot 2014-12-08 at 11 31 16 am](https://cloud.githubusercontent.com/assets/1529366/5343719/2adf1b3e-7ece-11e4-98c8-f6de5d573307.png)

## After
![screen shot 2014-12-08 at 11 31 28 am](https://cloud.githubusercontent.com/assets/1529366/5343718/2835e458-7ece-11e4-9c38-c7e44be39046.png)
I think this should be `1.9999999999999px` but I think that's just me.