Allow authorize or revoke security group rules in batch

Currently boto only lets you authorize or revoke one rule at a time. This costs more API calls than needed. In an automated process where we authorize a large number of rules in a short amount of time, we often hit API rate limit.

This pull request will batch all rules in one API call. Amazon API already supports multiple rules in one call.

http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-AuthorizeSecurityGroupIngress.html
http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-RevokeSecurityGroupIngress.html