code: function compareRssi(a,b) {
    if(a.rssi < b.rssi)
      return 1;
    if(a.rssi > b.rssi)
      return -1;
    return 0;
  }
docs: Compare rssi values for array sorting.
  @param {Object} a An rssiSignature entry.
  @param {Object} b Another rssiSignature entry.