Bump version in master to 9.0.0
Bump version in master to 9.0.0

Following our version numbering scheme
https://github.com/mozilla-services/screenshots/issues/2647

mozilla-services/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/screenshots,mozilla-services/screenshots