Added support for CocoaPods 0.36 & Swift frameworks.

Added a `module.modulemap` file which describes the framework and which Xcode requires for true frameworks to work correctly.

When using LayerKit with the upcoming version of CocoaPods (which supports Swift) this addition is also necessary or otherwise the project will no longer work for everyone.

For more details see discussion @ https://github.com/CocoaPods/swift/issues/4#issuecomment-66914260