docs: function get_cpu_idle() {
    var idle = 0;
    var cpus = os.cpus();
    var i, len;
    for (i=0, len = cpus.length; i < len; i += 1) {
      var cpu = cpus[i];
      var total = cpu.times.sys + cpu.times.idle + cpu.times.user + cpu.times.nice + cpu.times.irq;
      idle += (cpu.times.idle/total*100);
    }
    idle = idle / cpus.length;
    return idle;
  }