Add ready? method to aws VPC and Subnet models
[aws|rds] Support Iops parameter

Allow an RDS instance to be provisioned with an amount of
provisioned IOPS.
[xenserver] Updated models to have all attributes from version 6.2.0
[rackspace|queues] adding the queues getting started guide
openstack modifications

* add model and collection for security group rules
* add mock data for networks
* returns address in create_server mock
* proper security group rule mocks
* proper security group mocks
[rackspace] apply documentation edits
Allow custom Mock.not_implemented message
Add pending -> available transitions for AWS VPC and Subnets
Use OpenSSL::Digest instead of deprecated OpenSSL::Digest::Digest
Merge pull request #2473 from amatsuda/digest_digest

Use OpenSSL::Digest instead of deprecated OpenSSL::Digest::Digest
Merge pull request #2466 from sugarb/vpc_and_subnet_ready

Add ready? method to aws VPC and Subnet models
Merge pull request #2472 from zertico/updating_xen_server_attributes

[xenserver] Updated models to have all attributes from version 6.2.0
Merge pull request #2470 from stormsilver/rds_iops

[aws|rds] Support Iops parameter