Add simple .gitlab-ci.yml

- just testing gitlab-ci -> slack posting
6 jobs for master in 49 seconds
Status Job ID Name Coverage
  Build
passed #664
build_Go

00:00:33

 
  Test
passed #666
test_Go

00:00:16

 
  External
passed jenkins

00:00

passed jenkins

00:00:02

passed jenkins

00:00:02

passed jenkins

00:00:02