Replace 6.0-to-6.7.md with 6.0-to-6.8.md
Use gitlab-shell 1.9.3
Merge branch 'update/6.0-to-6.8' into 'master'

Replace 6.0-to-6.7.md with 6.0-to-6.8.md
Add NotesFinder spec
Notes have noteables but no commits
Fail faster on an invalid target_type
Filter out old notes in NotesFinder
Always set last_fetched_at in NotesFinder spec
Pass last_fetched_at for notes to javascript
Serialize last_fetched_at as a string with seconds
Add an index for Note#updated_at
Default last_fetched_at to 0 for old clients

Users who have not refreshed their browser tab will poll GitLab using
outdated JS. This change makes the server fall back to the old behavior
(send all comments) for old clients, instead of throwing an exception
for old clients.
Merge branch 'notes_finder_updated_at' into 'master'

NotesFinder filters by updated_at
Merge branch 'master' of https://github.com/gitlabhq/gitlabhq