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
Adding updated values for recurring autoscale operations
Adding updated documentation for the new variables
Improve docs for EC2_run_image and Image_run

- Fill in missing parameter description
- Include new instance types
Fixed a bug where URIs were properly canonicalized in Sig V4 signatures.
Added a high-level interface over DynamoDB v2.
Fixed a test failure involving connections.
Merge pull request #1489 from toastdriven/canonical-uri

Fixed a bug where URIs were properly canonicalized in Sig V4 signatures.
Add port to host header when necessary for signature V4
Added tests to verify the SigV4 port behavior.
Fix variable overwrite in build_put_params

Before this patch, the for loop at the bottom of `build_put_params`
would overwrite the passed in value variable, resulting in spurious
log messages:

    'You supplied a value and statistics for a metric. Posting
     statistics and not value.'

I've changed the variable name from value to val to prevent the
overwrite and stop the spurious log messages.
Added tests for the previous CloudWatch patch.
Merge pull request #1487 from arturhoo/ec2-doc-fix

Improve docs for EC2_run_image and Image_run
Updated Opsworks to add ELB support & handle the latest parameters.