Use a vendor directory for repeatable builds - fixes #816

This is using godep to manage the vendor directory.

vendor/bazil.org/fuse/unmount_linux.go

@@ -0,0 +1,21 @@
+package fuse
+
+import (
+	"bytes"
+	"errors"
+	"os/exec"
+)
+
+func unmount(dir string) error {
+	cmd := exec.Command("fusermount", "-u", dir)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		if len(output) > 0 {
+			output = bytes.TrimRight(output, "\n")
+			msg := err.Error() + ": " + string(output)
+			err = errors.New(msg)
+		}
+		return err
+	}
+	return nil
+}