code: function probe(addr, cb, config) {
      // Do not reassign function parameter
      var _config = config || {};
  
      return ping.probe(addr, _config).then(function (res) {
          cb(res.alive, null);
      }).catch(function (err) {
          cb(null, err);
      }).done();
  }
docs: TODO: 1. Port round trip time to this callback 2. However, it may breaks backward compatability 3. Need discussion 
  Callback after probing given host
  @callback probeCallback
  @param {boolean} isAlive - Whether target is alive or not
  @param {Object} error - Null if no error occurs
   
  Class::Ping construtor
  
  @param {string} addr - Hostname or ip addres
  @param {probeCallback} cb - Callback
  @param {PingConfig} config - Configuration for command ping