.travis.yml: fix for cmake
.travis.yml: fix for cmake

MrTheodor/csg,votca/csg,MrTheodor/csg,junghans/csg,MrTheodor/csg,votca/csg,junghans/csg,junghans/csg,junghans/csg,junghans/csg,votca/csg,votca/csg,MrTheodor/csg,MrTheodor/csg,junghans/csg