Change mock storage service to do case-insensitive header lookups.
Merge pull request #1594 from jterrace/mock-headers-case-insensitive

Change mock storage service to do case-insensitive header lookups.
Added support for the STS's ``DecodeAuthorizationMessage``.
Added some simple tests for Route53's ``ResourceRecordSets``.
PARTIAL: Started updating RDS to current.
Updated RDS to current.
Merge branch 'rds-update' into develop