Changed project to use Maven; lots of changes!

- Added pom.xml Maven file
- Removed Make (makefile) and Ant (build.xml) support
- Updated README
- Changed project package name to 'info.dustin_leavins.calculatord'
  to better reflect where CalculatorD comes from
- Tweaked .gitignore for Maven
- Changed tests! Maven sets up jUnit 3 by default, and tests needed to
  be changed to use this older version