Merge pull request #12 from davidfischer-ch/dev

Fix various PEP-8 warnings (etc)
Fix: Management command complains about wrong number of arguments when called.
Merge pull request #13 from mathieuhinderyckx/master

Fix: Management command complains about wrong number of arguments when c...
Update changelog.
Update version to 0.9.0
Merge branch 'master' into builder-v2