Release 1.9.0

In CHANGELOG:

- Add full HTTP metrics and logging to GitLab pages using LabKit !161

Not in CHANGELOG:

- Add golang 1.13 to the ci !176
- Convert vendoring to go modules. !164
- Update vendoring to latest !179
- Remove github.com/stretchr/testify/assert !180
- Rename confusing domain struct !184

#249 (closed)

All other changes were backstage: migrating to go-modules/refactoring.