docs: function PostgreStore(conString, options) {
      if(!conString){
          throw new Error('Connection String is missing.');
      }
  
      this._options = options || {};
      this._options.pgstore = this._options.pgstore || {};
      this._difficulty = this._options.pgstore.difficulty || 10;
  	this._table = this._options.pgstore.table || 'passwordless';
  
      this._client = new pg.Pool({
          connectionString: conString,
          max: this._options.pgstore.pgPoolSize || 10
      });
  
      if(!isNumber(this._difficulty) || this._cost < 1) {
          throw new Error('bcrypt difficulty must be an integer >= 1');
      }
  
      delete this._options.pgstore;
  
      var self = this;
      this._client.connect(function(err, client) {
          if(err) {
              throw new Error('Could not connect to Postgres database, with error : ' + err);
          }
      });
  }