require C++ compiler in travis
require C++ compiler in travis

kbarbary/sncosmo,dannygoldstein/sncosmo,sncosmo/sncosmo,dannygoldstein/sncosmo,dannygoldstein/sncosmo,sncosmo/sncosmo,kbarbary/sncosmo,kbarbary/sncosmo,sncosmo/sncosmo