Merge branch 'release' into 'master'

Release

release v0.4.0

See merge request !46
3 jobs for stable in 4 minutes and 14 seconds (queued for 2 minutes and 43 seconds)
Status Job ID Name Coverage
  Test
passed #2522
lint
test:lint

00:00:40

passed #2523
docker
test:py2.7

00:03:01

55.0%
passed #2524
docker
test:py3.4

00:02:47

55.0%