gmxtrajectorywriter: fix build with gmx-2017
gmxtrajectorywriter: fix build with gmx-2017

frame.bTitle was dropped in
gromacs/gromacs@953d3e7aa050a4a7076db723ebec14bf8d4c56a4

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