adjust postgres for heroku

postgres.js

@@ -1,11 +1,7 @@
 const Client = require('pg').Client
 
 const client = new Client({
-    user: '',
-    host: 'localhost',
-    database: 'contacts',
-    password: '',
-    port: 5432,
+    connectionString: process.env.DATABASE_URL || 'postgresql://localhost:5432/contacts',
 })
 
 module.exports = client;