Bump cassandra version in travis
Bump cassandra version in travis

iksaif/biggraphite,criteo/biggraphite,criteo/biggraphite,Thib17/biggraphite,criteo/biggraphite,Thib17/biggraphite,Thib17/biggraphite,Thib17/biggraphite,iksaif/biggraphite,iksaif/biggraphite,dpanth3r/biggraphite,iksaif/biggraphite,criteo/biggraphite