Add patterns for AWS S3 & ELB access log

Add grok pattern to parse S3 access logs, http://docs.aws.amazon.com/AmazonS3/latest/dev/LogFormat.html, and ELB access logs, http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/access-log-collection.html.
The same to_i is applied here, so this == 0.