Add request/parser for DescribeOperableDBInstanceOptions
Return boolean, not index of match.
Add model, collection for instance_options
Use correct filters in RDS model instance_options 'all' method
Merge branch 'master'
Merge branch 'master' of https://github.com/jbence/fog
Set up tests (and make them pass) for orderable_db_instance_options
Adjust number of items returned for test
Remove failure test; non-existent engine sometimes has options
Merge pull request #1951 from jbence/feature/AWS_RDS_DescribeOrderableDBInstanceOptions

[aws|rds] implement describe_orderable_db_instance_options