Use container-based infrastructure for travis-ci.
Use container-based infrastructure for travis-ci.

To start up faster.

mydongistiny/ninja,juntalis/ninja,sgraham/ninja,ndsol/subninja,mohamed/ninja,atetubou/ninja,moroten/ninja,lizh06/ninja,AoD314/ninja,martine/ninja,iwadon/ninja,bradking/ninja,ninja-build/ninja,maruel/ninja,AoD314/ninja,sxlin/dist_ninja,ninja-build/ninja,juntalis/ninja,atetubou/ninja,sgraham/ninja,bradking/ninja,moroten/ninja,ninja-build/ninja,vvvrrooomm/ninja,mgaunard/ninja,mgaunard/ninja,fuchsia-mirror/third_party-ninja,vvvrrooomm/ninja,ndsol/subninja,nafest/ninja,sxlin/dist_ninja,vvvrrooomm/ninja,juntalis/ninja,nicolasdespres/ninja,mydongistiny/ninja,nico/ninja,AoD314/ninja,fuchsia-mirror/third_party-ninja,sxlin/dist_ninja,maruel/ninja,moroten/ninja,nicolasdespres/ninja,sxlin/dist_ninja,AoD314/ninja,Qix-/ninja,mydongistiny/ninja,ndsol/subninja,Qix-/ninja,atetubou/ninja,maruel/ninja,martine/ninja,mgaunard/ninja,maruel/ninja,fuchsia-mirror/third_party-ninja,nafest/ninja,fuchsia-mirror/third_party-ninja,nico/ninja,iwadon/ninja,Maratyszcza/ninja-pypi,nico/ninja,atetubou/ninja,mgaunard/ninja,nicolasdespres/ninja,lizh06/ninja,mohamed/ninja,lizh06/ninja,moroten/ninja,ninja-build/ninja,nico/ninja,sxlin/dist_ninja,Qix-/ninja,Qix-/ninja,sxlin/dist_ninja,iwadon/ninja,martine/ninja,iwadon/ninja,bradking/ninja,juntalis/ninja,nicolasdespres/ninja,martine/ninja,Maratyszcza/ninja-pypi,ndsol/subninja,Maratyszcza/ninja-pypi,mohamed/ninja,sxlin/dist_ninja,Maratyszcza/ninja-pypi,sgraham/ninja,nafest/ninja,nafest/ninja,lizh06/ninja,bradking/ninja,mydongistiny/ninja,mohamed/ninja,vvvrrooomm/ninja,sgraham/ninja