Revert "Merge pull request #1683 from danielgtaylor/rds-vpc-sg"

This reverts commit 1b8d700f54a5247ff942d67cf5c436ffa5c4a301, reversing
changes made to b22091fa21d4925e54ed0146d2f205ceb36995e4.

dialt0ne's version of vpc + security groups for RDS is more complete.
rds support for vpc security groups (rebased on boto 0.10.0 master)
Add unit tests to dialt0ne's VPC implementation

Unit tests are based on those of danielgtaylor,
with additions for reading VpcSecurityGroup during
a call to get DB instance.
Example update and PEP8 fixes
Merge pull request #1694 from danielgtaylor/rds-vpc-sg2

A more comprehensive implementation of rds vpc security groups. Fixes #1694, #1685.