fix typo in example

Author: stomita

README.md

@@ -26,7 +26,7 @@ $ npm start
 When you use JSforce in your JavaScript app, set `proxyUrl` when creating `Connection` instance. 
 
 ```javascript
-var conn = jsforce.Connection({
+var conn = new jsforce.Connection({
   accessToken: '<access_token>',
   instanceUrl: '<instance_url>',
   proxyUrl: 'https://your-ajax-proxy-service.herokuapp.com/proxy/'