Update to client-go v3.0.0

Set delete propagation policy (to "foreground")

Kubernetes 1.6 adds a `PpropagationPolicy` to the delete options,
obsoleting the previous `OrphanDependents` boolean.

This change sets `PropagationPolicy=foreground`, keeping the legacy
`OrphanDependents=false` for older k8s servers.

Note that PropagationPolicy=background is broken in k8s 1.6 and (eg)
leaks pods from a deployment.  See kubernetes/kubernetes#44046 for
upstream discussion.

Add 'subset' diff stategy option that checks the live state is a subset of the config state.

Anonymously import the GCP auth provider to get the registration side effect.

Register *all* auth plugins (gcp + oidc)

Fix deploy runtime version check harder

Travis' deploy.on golang version check seems to be surprising.  In
particular `deploy.on.go=1.8.x` will *not* match a build performed
with `go=['1.8.x']`.

This change just gives up and uses an explicit bash conditional.
Uglier, but fewer surprises.

Update to newer xcode for travis osx builds

Frequent `make test` crashes on (default) xcode7.3 in jsonnet_cgo. Use
a different/newer build environment.

Fix go point-release version references

Prefer `1.8.x` rather than `1.8`.  In particular `deploy.on.go=1.8` does
not match (eg) `1.8.3` :(

Update to client-go release-3

Switch logging from glog to logrus

Add per-file license headers

Improve interactive output experience by switching to a logging
library (logrus) that allows customising the output format.

This also removes the glog command line flags.  Replaced with a
simpler `--verbose`/`-v` option:
- quiet by default (warnings and errors only)
- `-v` for progress info
- `-vv` for debug

Fixes #34

Fixes #35

More complete implementation of extvars, topvars

Fix goreportcard-reported lint issues

- `gofmt -s utils/registry_test.go`
- Fix missing `if err != nil` check in `cmd/delete.go` (a bug, but not critical)
- Add goreportcard button to README

Replace quickstart example with something that works

Add several regex native functions

Rename --extVar to --ext-str

- `escapeStringRegex`
- `regexMatch`
- `regexSubst`

They do what you expect, as implemented by the golang `regexp` package.

For consistency with other options (hyphenated, not camel case), and
the upstream `jsonnet` tool.

This allows you to actually reach the guestbook in most environments
without further changes (including minikube, since LoadBalancer
implies NodePort).