Fix creation of Pool with connection string passed by string

Author: denchistyakov

lib/index.js

@@ -15,6 +15,9 @@ var Pool = require('pg-pool')
 
 const poolFactory = (Client) => {
   var BoundPool = function (options) {
+    if (typeof options === 'string') {
+      options = { connectionString: options }
+    }
     var config = Object.assign({ Client: Client }, options)
     return new Pool(config)
   }