Fixing documentation errors in the DBParameterGroup methods
Update __init__.py

Support for VPC Security Groups in RDS deployments
Rename vpc_security_groups_ids -> vpc_security_groups for consistency with security_groups option; Modify behavior to allow passing in SecurityGroup instances from EC2.
Documentation fixes
Add unit tests for vpc_security_groups when creating RDS database instances.
Merge pull request #1683 from danielgtaylor/rds-vpc-sg

[RDS] VPC Security Group Support. Fixes #1683, #1602.
Fixed a small typo in the SQS tutorial.
Merge pull request #1684 from cornmander/sqs-tutorial-typo

Fixed a small typo in the SQS tutorial.
Use transcoding-invariant headers when available in gs.Key
correct start of month in trim_snapshots docstring

Monthly snapshots are from the first day of each month, whereas the
old docstring indicated they were from the first Sunday of each month.
add trim_snapshots option to limit number of monthly backups
Add unit tests for trim_snapshots defeault behavior and test the new monthly backups feature
Merge pull request #1688 from danielgtaylor/andrewyates-develop

[EC2] Add monthly_backups argument to trim_snapshots. Fixes #1688, #1612.
Merge pull request #1682 from mveitas/develop

Fixing documentation errors in the DBParameterGroup methods
Start moving get_all_instances to get_all_reservations

get_all_instances doesn't actually get all instances, but rather gets
all *reservations*, which themselves contain instances.  This commit
starts the process of making get_all_instances actually return a list of
instances by doing a few things:

1. Rename the current get_all_instances to get_all_reservations.
2. Make get_all_instances a stub that warns and then calls
   get_all_reservations.
3. Add a new get_only_instances method that will eventually become the
   new behavior of get_all_instances.

People can then transition to get_all_reservations and
get_only_instances as appropriate until get_all_instances finally
switches over in a future release.