Removes MotionMap dependency

There are two motivations for this change. The first is that the MotionMap requirement seems to sometimes create dependency issues for users (though I believe that has been fixed in the most recent version).

The second reason is that instantiating a `MotionMap::Map` is over an order-of-magnitude slower than instantiating a simple hash. This inefficiency led me to override some of the methods of this gem in my own project. For the mild benefit of the helper methods that MotionMap provides, I don't think it significantly improves the code cleanliness enough to warrant the decrease in performance from using a regular hash. Actually, I'd argue that using a hash is more readable, especially for someone with no experience with MotionMap.

I also cleaned up some whitespace in the tests and fixed ones that were broken. I couldn't get the tests or sample app to run without also updating `motion-cocoapods`, but if you think this gem update shouldn't have been necessary, let me know.