ci: remove Travis CI

.travis.yml

@@ -1,22 +0,0 @@
-dist: trusty
-sudo: required
-
-env:
-  matrix:
-  - TEST_TARGET: test-debian
-  - TEST_TARGET: test-alpine
-
-before_install:
-  - sudo apt-get -y remove docker docker-engine docker-ce
-  - sudo rm /etc/apt/sources.list.d/docker.list
-  - 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 install docker-ce
-  - docker version
-  - docker info
-  # prepare docker test requirements
-  - make update-dependencies
-
-script:
-  - make $TEST_TARGET