Update README.md

Author: rehrumesh

README.md

@@ -149,17 +149,17 @@ var AWS = require('aws-sdk');
 new AWS.DynamoDB.DocumentClient({
     region: 'localhost',
     endpoint: 'http://localhost:8000',
-    accessKeyId: 'bogusaccesskeyid',  // needed if you don't have aws credentials at all in env
-    secretAccessKey: 'bogussecretaccesskey' // needed if you don't have aws credentials at all in env
+    accessKeyId: 'DEFAULT_ACCESS_KEY',  // needed if you don't have aws credentials at all in env
+    secretAccessKey: 'DEFAULT_SECRET' // needed if you don't have aws credentials at all in env
 })
 ```
 e.g. for dynamodb document client sdk
 ```
 new AWS.DynamoDB({
     region: 'localhost',
     endpoint: 'http://localhost:8000',
-    accessKeyId: 'bogusaccesskeyid',  // needed if you don't have aws credentials at all in env
-    secretAccessKey: 'bogussecretaccesskey' // needed if you don't have aws credentials at all in env
+    accessKeyId: 'DEFAULT_ACCESS_KEY',  // needed if you don't have aws credentials at all in env
+    secretAccessKey: 'DEFAULT_SECRET' // needed if you don't have aws credentials at all in env
 
 })
 ```