Changed tintColor on accessory view for iOS7 and up

We've conditionally set the `tintColor` on the input accessory view's items.

tintColor exists on the classes in iOS6 so the code compiles under Xcode 4.6.

![screen shot 2013-09-21 at 11 31 53 pm](https://f.cloud.github.com/assets/17407/1185730/7da103f4-22c3-11e3-98b8-8288efc6a3ef.png)