Fixed most hairlines for iPhone6 plus and other retina devices

Before and after screenshots below.

Hairlines are more consistent throughout and also now visible in the browser (chrome when you set iPhone6 plus emulation).

TODO: Figure out how to improve hairlines for input boxes (messagebar and prompt) without impacting style or performance.


![screen shot 2014-12-14 at 11 14 16 am](https://cloud.githubusercontent.com/assets/5016637/5428017/8ad7b1d2-8382-11e4-891b-4de2d132bc5b.png)
![screen shot 2014-12-14 at 11 15 12 am](https://cloud.githubusercontent.com/assets/5016637/5428016/8ad73572-8382-11e4-9a45-be78d4bfdc13.png)

 

![ios simulator screen shot dec 14 2014 11 09 35 am](https://cloud.githubusercontent.com/assets/5016637/5427967/128566f2-8382-11e4-9aa3-060c9b378d73.png)
![ios simulator screen shot dec 14 2014 11 04 02 am](https://cloud.githubusercontent.com/assets/5016637/5427968/128a185a-8382-11e4-98d4-6341d3dacba4.png)
![ios simulator screen shot dec 14 2014 11 09 45 am](https://cloud.githubusercontent.com/assets/5016637/5427969/128d7284-8382-11e4-8af5-8f6f3940dbd9.png)
![ios simulator screen shot dec 14 2014 11 05 03 am](https://cloud.githubusercontent.com/assets/5016637/5427970/12918126-8382-11e4-9ad2-b20d98357e56.png)