Several additions

Hello,

After testing current implementation on a pretty big project with a dozen of different parcelable classes I came to a conclusion that some things need to change.

First of all, wrapper classes such as Boolean, Long etc need to be null-safe. If you pass null to writeLong, you'll get an exception. I'll also modified List transformer to produce null-safe code.

Next, readValue should use Class#getClassLoader() instead of null (null means default classloader). I'm not quite sure why this is happening, but if your app is relaunched after being destroyed, default classloader just won't do and you'll get a ClassNotFound exception.

And I've also added transformers for JSON because why not.