This commit adds a Makefile rule for installing the vendor directory.
Both the `build` and `docker-build` phony rules depend on the `vendor`
rule, which in turn depends on the `glide.lock` rule. This means that
any time the `glide.lock` file is updated, the vendor directory will be
re-installed.
The `build` Makefile target attempted to place the generated artifact in
`/build`, where it should have used a local directory instead. This
commit makes the directory configurable using the `OUT_DIR` argument,
and defaults it to ./_output
k8s.io/custom-metrics-boilerplate was "renamed" to
"github.com/directxman12/custom-metrics-boilerplate". This updates all
references to point to the correct location.
This commit instruments prometheus query times by prometheus endpoint,
allowing us to see how quickly prometheus answers the queries that
back the custom-metrics API endpoints.
The initial functionality works. There's still a number of TODOs to
clean up, and some edge cases to work around, and some errors that could
be handled better.
