Support auto layout by setting child frames when layoutSubviews happens, also added podspec file

[jkoehl]

I think this is required to make the field properly layout its subviews when it is inside of a view that is using auto-layout. Without this I found that as auto-layout adjusted the TokeFieldView's frames it was not updating its child layout.

I also, added a podspec file. Technically not related but without the podspec file in the repo it is a bit harder to work with in Cocoapods.

[thermogl]

Cool - Thanks :)