Add log shim and collect command

The collect command redirects function logs to the journal for
viewing on journalctl. faas-cli logs is not implemented as of
yet. View logs with journalctl -t openfaas-fn:FN_NAME_HERE.

Tested on Dell XPS with Ubuntu Linux. The approach takes
inspiration from the Stellar project.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

cmd/root.go

@@ -18,6 +18,10 @@ func init() {
 	rootCommand.AddCommand(collectCmd)
 }
 
+func RootCommand() *cobra.Command {
+	return rootCommand
+}
+
 var (
 	// GitCommit Git Commit SHA
 	GitCommit string