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/prometheus/procfs/.gitignore

@@ -0,0 +1 @@
+/fixtures/

vendor/github.com/prometheus/procfs/scripts/check_license.sh

@@ -1,29 +0,0 @@
-#!/bin/sh
-#
-# Copyright 2018 The Prometheus Authors
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-# http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-check_license() {
-  local file=""
-  for file in $(find . -type f -iname '*.go' ! -path './vendor/*'); do
-    head -n3 "${file}" | grep -Eq "(Copyright|generated|GENERATED)" || echo "  ${file}"
-  done
-}
-
-licRes=$(check_license)
-
-if [ -n "${licRes}" ]; then
-  echo "license header checking failed:"
-  echo "${licRes}"
-  exit 255
-fi

vendor/github.com/prometheus/procfs/sysfs/.gitignore

@@ -0,0 +1 @@
+fixtures/