remove 17.0rc1 from travis, wait for travis 17.0 support
remove 17.0rc1 from travis, wait for travis 17.0 support

umatomba/relx,timclassic/relx,priestjim/relx,ingwinlu/relx,bitwalker/relx,erlware/relx,syl20bnr/relx,zugolosian/relx,bsmr-erlang/relx,Licenser/relx,ethercrow/relx,lrascao/relx,tsloughter/relx,RJ/relx