Merge branch 'wip-ci' into 'master'

Add .gitlab-ci.yml: tests and style checking

See merge request !116
2 jobs for master in 9 minutes and 15 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #297325
volatile linux
check

00:05:54

passed #297326
volatile linux
test

00:09:14