func GetLoadAvg() (LoadAvg, error) {
	txt, err := readLoadAvg()
	if err != nil {
		return LoadAvg{}, err
	}
	return getLoadAvg(txt)
}
GetLoadAvg reads '/proc/loadavg'.
Expected output is '0.37 0.47 0.39 1/839 31397'.
package proc
import (
	"fmt"
	"io/ioutil"
	"strconv"
	"strings"
	"github.com/gyuho/linux-inspect/pkg/fileutil"
)
type loadAvgColumnIndex int
const (
	load_avg_idx_load_avg_1_minute loadAvgColumnIndex = iota
	load_avg_idx_load_avg_5_minute
	load_avg_idx_load_avg_15_minute
	load_avg_idx_kernel_scheduling_entities_with_slash
	load_avg_idx_pid
)