drop squeak-5.0 from travis. apparently it lacks includesSubstring:
drop squeak-5.0 from travis. apparently it lacks includesSubstring:

https://travis-ci.org/HPI-SWA-Lab/BP2016H1/jobs/231513660

HPI-SWA-Lab/BP2016H1,HPI-SWA-Lab/BP2016H1,HPI-SWA-Lab/BP2016H1,HPI-SWA-Lab/BP2016H1,HPI-SWA-Lab/BP2016H1