upgrade travis to use container based service for faster builds
upgrade travis to use container based service for faster builds

otadmor/Open-Knesset,MeirKriheli/Open-Knesset,OriHoch/Open-Knesset,noamelf/Open-Knesset,otadmor/Open-Knesset,MeirKriheli/Open-Knesset,alonisser/Open-Knesset,daonb/Open-Knesset,OriHoch/Open-Knesset,daonb/Open-Knesset,noamelf/Open-Knesset,navotsil/Open-Knesset,alonisser/Open-Knesset,MeirKriheli/Open-Knesset,otadmor/Open-Knesset,noamelf/Open-Knesset,navotsil/Open-Knesset,alonisser/Open-Knesset,daonb/Open-Knesset,daonb/Open-Knesset,OriHoch/Open-Knesset,alonisser/Open-Knesset,MeirKriheli/Open-Knesset,noamelf/Open-Knesset,navotsil/Open-Knesset,navotsil/Open-Knesset,otadmor/Open-Knesset,OriHoch/Open-Knesset