fix(*): Vendored project dependencies

vendor/github.com/acomagu/bufpipe/README.md

@@ -0,0 +1,42 @@
+# bufpipe: Buffered Pipe
+
+[![CircleCI](https://img.shields.io/circleci/build/github/acomagu/bufpipe.svg?style=flat-square)](https://circleci.com/gh/acomagu/bufpipe) [![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg?style=flat-square)](https://godoc.org/github.com/acomagu/bufpipe)
+
+The buffered version of io.Pipe. It's safe for concurrent use.
+
+## How does it differ from io.Pipe?
+
+Writes never block because the pipe has variable-sized buffer.
+
+```Go
+r, w := bufpipe.New(nil)
+io.WriteString(w, "abc") // No blocking.
+io.WriteString(w, "def") // No blocking, too.
+w.Close()
+io.Copy(os.Stdout, r)
+// Output: abcdef
+```
+
+[Playground](https://play.golang.org/p/PdyBAS3pVob)
+
+## How does it differ from bytes.Buffer?
+
+Reads block if the internal buffer is empty until the writer is closed.
+
+```Go
+r, w := bufpipe.New(nil)
+
+done := make(chan struct{})
+go func() {
+	io.Copy(os.Stdout, r) // The reads block until the writer is closed.
+	done <- struct{}{}
+}()
+
+io.WriteString(w, "abc")
+io.WriteString(w, "def")
+w.Close()
+<-done
+// Output: abcdef
+```
+
+[Playground](https://play.golang.org/p/UppmyLeRgX6)