Initial support for DBSubnetGroup
_sign_string private_key_file can now be file-like

Distribution._sign_string is now a little bit more flexible, allowing
the private_key_file to be a file-like object (or really anything with a
.read() method).
Added support for block device mappings in autoscaling groups (re #753, #1343)
updat incorrect copyright
Add missing function parameter (re: #1357)
add integration test
cloudformation Stack DisableRollback is always True

Fix problem where DisableRollback is always true, because
bool("False") == True
Merge branch 'develop' of git://github.com/boto/boto into dbsubnetgroup
Fix CloudFront docs to match current reality.

CloudFront's create_distribution requires origin object. To match
the spirit of the docs, update docs to reflect creating the S3Origin
object first.

This might be worse than just assuming (and documenting) that passing a
string into origin for create_distribution implies
S3Origin(dns_name='thestr'). Design decision left for later.
Added DkimTokens as a list marker.
Add MinAdjustmentType for autoscaling.

When policy_type is PercentChangeInCapacity, allows values of
min_adjustment_type, which set the AWS MinAdjustmentType value for
autoscaling policies.
Add mobile push API
Add unit tests for publish operation
Add target_arn to publish method in SNS client
add region suppoer for elbadmin
Added public IP in VPC support to EC2.
Added support for the STS's ``DecodeAuthorizationMessage``.
Added some simple tests for Route53's ``ResourceRecordSets``.
Update url explaining base64 SQS messages.
PARTIAL: Started updating RDS to current.