Task: Update README

* pass options through to SQS constructor

README.md

@@ -15,11 +15,20 @@ npm install sqs-producer --save
 ```js
 var Producer = require('sqs-producer');
 
+// create simple consumer
 var producer = Producer.create({
   queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
   region: 'eu-west-1'
 });
 
+// create custom producer (supporting all opts as per the API docs: http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SQS.html#constructor-property)
+var producer = Producer.create({
+  queueUrl: 'https://sqs.eu-west-1.amazonaws.com/account-id/queue-name',
+  region: 'eu-west-1'
+  accessKeyId: 'yourAccessKey',
+  secretAccessKey: 'yourSecret'
+});
+
 // send messages to the queue
 producer.send(['msg1', 'msg2'], function(err) {
   if (err) console.log(err);