Mavenization, restructuring project into 'library' and 'demo' folders, fix for #50

Hi, I have added Maven support to your project, it will help people (like us in @inmite) which need to maintain all dependencies via maven or graddle.

If you want to build with maven you need to:
- locally install newest support library using https://github.com/mosabua/maven-android-sdk-deployer
- locally install date4j library jar (or deploy it into some public repo like Maven Central)