Upstream changes, Travis-CI and SLF4J

* Remove GraphHopper dependency. Now everything is handled using JGraphT
* Change graphhopper-sna depency to Java Network Analyzer (the project was renamed and now uses JGraphT rather than GraphHopper)
* Build on Travis-CI (The .travis.yml will have to be updated for the IRSTV)
* Use SLF4J for logging

TODO:
* Add more tests
* Move all System.out.println's to logs