from_sns is required when using SQS

[shane-od]

TypeError: no implicit conversion of nil into String

is thrown when you're using an SQS queue and you don't define the "from_sns" option as false. Fails on this line: payload = JSON.parse(payload['Message']) if @from_sns

[richard-mauri]

This seems to be a duplicate of: #57
I noticed this as I am preparing a POC with this component; I am not a responsible contributor