Add cocoapods support

I've written a simple podspec here. The new LICENSE file is used to meet the requirement of Cocoapods.

Here are some tasks to do to make this SDK fully support cocoapods integration:
1. Add a tag to each release version
2. Change the source configuration in podspec (Line 57)
3. Push to the Cocoapods Spec Repo (via ```pod``` command)

'-beta<number>' for now?