Updates SQS service hook - now with more region control!

It had been awhile since the SQS service hook had seen some love. The approach for modernization is outlined in issue #735 and more details are there.

Briefly, this PR:

+ removed the right_aws gem dependency in favor of the official aws-sdk gem maintained by Amazon (and used in the Amazon SNS hook).
+ updates the form (front-end) for users explaining how to find the arn
+ maintains backward compatibility for folks who are using the hook with `sqs_queue_name`
+ fixes bug I found in the README

I tested in the console and ... it works! I wasn't sure how to test for backward compatibility completely. In the console, I passed in `sqs_queue_name` when initializing the service and it worked. I assume that the `white_list` and password methods in the main service class fetch and pass in their values on initialization. Please be sure to double check my work on this.

I also assume that removing `:sqs_queue_name` from the `string` method removes it from the form. I wasn't able to test that though.

Other than that, this thing should be :cake: and :beer: