Merge branch 'release-0.8.1'

Merge branch 'release-0.8'

Merge branch 'release-0.7'

Merge branch 'release-0.6.1'

Merge branch 'release-0.6'

Merge branch 'release-0.5'

v0.4.1

Major improvements:

- Adding 'check_relationship' parameter to also check foreign key diffs,
- Adding travis integration