For all the examples, create pvc using `pvc.yaml` first.

The permission of directory is 0770, because when a user login as group
e.g. group 1000, they're also belong to group 0. The default permission
for host path is 0700, which prevent group 0 from accessing the directory.

Fixes https://github.com/rancher/local-path-provisioner/issues/7 .

Also added test case `security-context.yaml` derived from @unguiculus 's
comment on the issue.

Remove Troubleshooting section for v1.11.

Also remove support for Kubernetes v1.11.

Fix provisioner to work with v1.12

Add uninstall

Refresh every 5 seconds by default

In order to setup default config.