delete tempfiles more reliably

hopefully, but it's an improvement. :)

go/linguaevalia/linguaevalia.go

	// write code to temp file
	f, err := writeCode(code, lang.Extension())
	defer f.Close()
	defer os.Remove(f.Name())
	if err != nil {
		return nil, err
	}
	if err != nil {
		return res, err
	}
	// remove the file
	os.Remove(f.Name())
	// return output
	return res, nil
}