Migrated to gradle
Introduced retrofit and rxJava for rest calls. Cleaned model and introduced gson for json processing.
Code clean up
Added readme again
Added screenshot to readme
Scaled screenshot
Deleted screenshot
Readded screenshot
Replace screenshot with jpg
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/de/fuelmeup/CarMapFragment.java
	src/de/fuelmeup/rest/Client.java