chore: update docker (#703)

Author: eshanholtz

.travis.yml

@@ -1,6 +1,11 @@
 language: java
 jdk: openjdk8
 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 -y -o Dpkg::Options::="--force-confnew" install docker-ce
+- docker --version
 - echo $GPG_SECRET_KEYS | base64 --decode | $GPG_EXECUTABLE --import --batch || true
 - echo $GPG_OWNERTRUST | base64 --decode | $GPG_EXECUTABLE --import-ownertrust --batch || true
 env: