digest/sha2 was required for sqs to connect successfully

https://logstash.jira.com/browse/LOGSTASH-1565

My colleague Zach Walls noticed this error with the 1.2.2 jars available:

Unable to access SQS queue 'Logstash_Testing_Queue': uninitialized constant Digest::SHA256 {:level=>:error}

We ended up trying the latest source and had the same issue. Eventually added digest/sha2 requirements to both input and output sqs.rb file which allowed us to connect to SQS again.