Version v9.4.0-rc.2

- Warn on archiving git directory !591
- Use Go 1.8 for CI !620
- Add CacheClient with timeout configuration for cache operations !608
- Remove '.git/hooks/post-checkout' hooks when using fetch strategy !603
- Update linux-repository.md !624
- Fix VirtualBox and Parallels executors registration bugs !589
- Support Kubernetes PVCs !606
- Support cache policies in .gitlab-ci.yml !621
- Improve kubernetes volumes support !625
- Fix incorrect substitute example in hostname in docker.md !627
- Fix typo in debug !630
- Adds an option `--all` to unregister command !622
- Add the techical description of version release !631
- Update documentation on building docker images inside of a kubernetes cluster. !628
- Support for extended docker configuration in gitlab-ci.yml !596
