Convert to Go modules (#1178)

* Convert to Go modules

* Update promu config.
* Convert to Go modules.
* Update vendoring.
* Update Makefile.common.
* Update circleci config.
* Use Prometheus release tar for promtool.
* Fixup unpack

* Use temp dir for unpacking tools.
* Use BSD compatible tar command.
* OpenBSD mkdir doesn't support `-v`.

Signed-off-by: Ben Kochie <superq@gmail.com>

vendor/github.com/mdlayher/genetlink/.travis.yml

@@ -0,0 +1,16 @@
+language: go
+go:
+  - 1.x
+os:
+  - linux
+sudo: required
+before_install:
+  - go get github.com/golang/lint/golint
+  - go get honnef.co/go/tools/cmd/staticcheck
+  - go get -d ./...
+script:
+  - go build -tags=gofuzz ./...
+  - go vet ./...
+  - staticcheck ./...
+  - golint -set_exit_status ./...
+  - go test -v -race -tags=integration ./...