Merge branch 'wip-ci' into 'master'

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

See merge request !116
2 jobs for 0.7 in 6 minutes and 41 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #297542
volatile linux
check

00:02:31

passed #297543
volatile linux
test

00:04:09