Add link to implementation for CockroachDB

[stephenafamo]

No description provided.

[elithrar]

Thanks for this - I did however notice that your README example opens a new connection for every client request, as well as leaking goroutines.

I suggest pulling these lines out into the main() of your program:

	// Fetch new store.
	store, err := crdbstore.NewCrDBStore("postgres://user:password@127.0.0.1:5432/database?sslmode=verify-full", []byte("secret-key"))
	if err != nil {
		log.Fatalf(err.Error())
	}
	defer store.Close()

	// Run a background goroutine to clean up expired sessions from the database.
	defer store.StopCleanup(store.Cleanup(time.Minute * 5))

[stephenafamo]

Thanks for pointing that out.

I've updated the example accordingly.

[elithrar]

Merged, thanks!