add required sudo for travis

.travis.yml

@@ -1,10 +1,11 @@
 language: minimal
+sudo: required
 services:
 - docker
 before_install:
 - curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
 - sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
-- sudo apt-get update
+- sudo apt-get -q update
 - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
 addons:
   apt: