Action sheet picker update (iOS8 compatibility)

Hi! First of all, thanks for the great work!

I understand you don't really want to maintain this library, but I just wanted to say I digged the whole github and found this is the greatest form lib with its simple elegancy of property mapping and seems lonely with the inline validation messages in its cells.

I just made two little modification and with them it seems fully iOS 8 compatible. The first one is just an action sheet picker update - don't be scared, a lot of change is just because the Vendor folder update.
The second one will come in an another pull request.

Cheers :)

![before](https://cloud.githubusercontent.com/assets/8742665/4780294/661916bc-5c61-11e4-9a49-138ebbe08644.png)
![after](https://cloud.githubusercontent.com/assets/8742665/4780295/661f2e8a-5c61-11e4-95b7-45596bd0468a.png)