Changed to new github services guidelines.
If sns_topic contains ARN, don't create it, just use it.
Made corrections in "How to test your service".

Instructions given were missing crucial `lib/` prefix.
Supports posting to multiple rooms if ids are used

Both room_id and room_name is supported so a check if needed to avoid breaking backward compatibility with rooms having comma in their name.
Only separate rooms if all are integers (i.e. room ids instead of room names).
Merge pull request #549 from paxan/patch-1

README corrections
Merge pull request #547 from paxan/sns-be-least-privileged

Allow payload to be published via AWS SNS with least amount of privileges
Merge pull request #550 from theill/master

Adds support for posting to multiple rooms by specifying room ids separated with comma
Merge pull request #500 from treeder/master

IronMQ service hook.
fix ruby syntax error

/cc @treeder