Travis config change - clean before build
Travis config change - clean before build

jforge/JavaHamcrest,mnk/hamcrest,wgpshashank/JavaHamcrest,mmichaelis/JavaHamcrest,alb-i986/JavaHamcrest,mmichaelis/JavaHamcrest,tomwhoiscontrary/JavaHamcrest,dkomanov/JavaHamcrest,rysh/JavaHamcrest,akruijff/JavaHamcrest,akruijff/JavaHamcrest,vizewang/JavaHamcrest,mnk/hamcrest,wgpshashank/JavaHamcrest,vizewang/JavaHamcrest,alb-i986/JavaHamcrest,plow/JavaHamcrest,tomwhoiscontrary/JavaHamcrest,rysh/JavaHamcrest,jforge/JavaHamcrest,plow/JavaHamcrest,dkomanov/JavaHamcrest