Use a vendor directory for repeatable builds - fixes #816

This is using godep to manage the vendor directory.

vendor/github.com/spf13/cobra/doc/man_docs.md

@@ -0,0 +1,26 @@
+# Generating Man Pages For Your Own cobra.Command
+
+Generating man pages from a cobra command is incredibly easy. An example is as follows:
+
+```go
+package main
+
+import (
+	"github.com/spf13/cobra"
+	"github.com/spf13/cobra/doc"
+)
+
+func main() {
+	cmd := &cobra.Command{
+		Use:   "test",
+		Short: "my test program",
+	}
+	header := &cobra.GenManHeader{
+		Title: "MINE",
+		Section: "3",
+	}
+	doc.GenManTree(cmd, header, "/tmp")
+}
+```
+
+That will get you a man page `/tmp/test.1`