add a basic podspec for INKFramework

Hey guys - you should consider creating a podspec for your framework since a lot of people use cocoapods to *search* and include library code for ios projects. It also will generate docs for you. Here is an example you guys can work from. I did this pretty quickly but I think it should work, I would just make sure to test that resources are resolved correctly via the bundle.

When it's ready you can submit a pull request to the CocoaPods repot to have it made available in the pod search index. 
https://github.com/CocoaPods/Specs/