Add fix for podspec git source attribute

In order to allow the podspec to lint properly, this commit adds the git
extension to the source url. It also adds a changelog to keep track of
changes across versions and updates the readme to show the latest
version of the pod.
Merge pull request #2 from endoze/add-git-to-podspec-git-source-to-fix-lint

Add fix for podspec git source attribute