Fix VPC security group rule bugs and update version number.

- Update version number in __init__.py to match package version 0.2.1.
- Fix bugs with SecurityGroupEgress and SecurityGroupIngress.
  - They are really only AWSProperty and not AWSObject derivatives.
  - They were generating bad JSON for VPC security group ingress/egress rules.
- Added workaround for AWS bug with SecurityGroupEgress rules.
  - Egress rules targeting a security group do not respect DestinationSecurityGroupId.
  - You have to use SourceSecurityGroupId to create these types of rules.
  - Added SourceSecurityGroupId to hash of allowed properties for SecurityGroupEgress.
  - This is a known AWS bug with EC2/CloudFormation APIs since mid-2012.
- All tested and verified working now.