Travis CI: The 'sudo' tag is now deprecated (#4542)
Travis CI: The 'sudo' tag is now deprecated (#4542)

[Travis are now recommending removing the __sudo__ tag](https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration).

"_If you currently specify __sudo: false__ in your __.travis.yml__, we recommend removing that configuration_"
stephanie-wang/ray,atumanov/ray,stephanie-wang/ray,stephanie-wang/ray,richardliaw/ray,ray-project/ray,atumanov/ray,atumanov/ray,pcmoritz/ray-1,stephanie-wang/ray,atumanov/ray,pcmoritz/ray-1,ray-project/ray,richardliaw/ray,ujvl/ray-ng,ray-project/ray,richardliaw/ray,ray-project/ray,robertnishihara/ray,atumanov/ray,robertnishihara/ray,pcmoritz/ray-1,pcmoritz/ray-1,ray-project/ray,robertnishihara/ray,ujvl/ray-ng,atumanov/ray,robertnishihara/ray,pcmoritz/ray-1,robertnishihara/ray,richardliaw/ray,ray-project/ray,ray-project/ray,robertnishihara/ray,ujvl/ray-ng,stephanie-wang/ray,richardliaw/ray,stephanie-wang/ray,pcmoritz/ray-1,richardliaw/ray,stephanie-wang/ray,stephanie-wang/ray,stephanie-wang/ray,ray-project/ray,richardliaw/ray,robertnishihara/ray,ujvl/ray-ng,pcmoritz/ray-1,robertnishihara/ray,atumanov/ray,robertnishihara/ray,richardliaw/ray,atumanov/ray,pcmoritz/ray-1