Add self-contained gometalinter build tooling.

tools/vendor/github.com/dchest/safefile/README.md

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+# safefile
+
+[![Build Status](https://travis-ci.org/dchest/safefile.svg)](https://travis-ci.org/dchest/safefile) [![Windows Build status](https://ci.appveyor.com/api/projects/status/owlifxeekg75t2ho?svg=true)](https://ci.appveyor.com/project/dchest/safefile)
+
+Go package safefile implements safe "atomic" saving of files.
+
+Instead of truncating and overwriting the destination file, it creates a
+temporary file in the same directory, writes to it, and then renames the
+temporary file to the original name when calling Commit.
+
+
+### Installation
+
+```
+$ go get github.com/dchest/safefile
+```
+
+### Documentation
+
+ <https://godoc.org/github.com/dchest/safefile>
+
+### Example
+
+```go
+f, err := safefile.Create("/home/ken/report.txt", 0644)
+if err != nil {
+	// ...
+}
+// Created temporary file /home/ken/sf-ppcyksu5hyw2mfec.tmp
+
+defer f.Close()
+
+_, err = io.WriteString(f, "Hello world")
+if err != nil {
+	// ...
+}
+// Wrote "Hello world" to /home/ken/sf-ppcyksu5hyw2mfec.tmp
+
+err = f.Commit()
+if err != nil {
+    // ...
+}
+// Renamed /home/ken/sf-ppcyksu5hyw2mfec.tmp to /home/ken/report.txt
+```