Travis - add PLY runtime dependency
Travis - add PLY runtime dependency

Looks like a new runtime dependency was introduced: https://github.com/FreeCAD/FreeCAD/commit/53bbf09bf9a624428808c2d528949092adb6fdbf
Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master