chore(.travis.yml): remove -O2 from cov build
chore(.travis.yml): remove -O2 from cov build

dreal/dreal4,dreal/dreal4,soonho-tri/dreal4,dreal/dreal4,soonho-tri/dreal4,soonho-tri/dreal4,soonho-tri/dreal4,dreal/dreal4