Update EMR API model
Update OpsWorks API model for VPC support
Updated Amazon RDS API to support tagging and filters
Various fixes to Amazon S3 API model

* Added MFA and VersionId inputs to S3.deleteObject()
* Added Prefix input and CommonPrefixes output to
  S3.listMultipartUploads()
Various fixes to integration test suite runner
Added support for modifying Amazon EC2 Reserved Instances.
Bump EC2 API version to 2013-08-15
Update EC2 API version in README
Bump version to v1.6.0
Add support for skipping removed API versions
S3 DeleteMarker parameter should be a boolean type
Add sitemap plugin to .yardopts