Merge branch 'release-0.66.0' into develop

* release-0.66.0:
  Bumping version to 0.66.0
  Updated JSON models
Update retryhandler to handle change in error response structures

Updated unit tests as well.
Merge branch 'retry-error-codes' into develop

* retry-error-codes:
  Update retryhandler to handle change in error response structures
Handle case where only type key is defined in waiters

There's an issue where the acceptor type is defined in __defaults__
but no other values for failure is defined.  This causes undefined
behavior for us and results in any waiter config that has an
acceptor_type defined in a parent config but no explicit failure_*
values throwing an exception when used.

The fix is not ignore these specific waiter configs.
Search for files in order of get_search_paths()

The reversed order was originally because we would recursively
merge in subsequent files with the same name, which made overrides
simpler.  Given we no longer do this recursive merge, we should
be iterating in the order given by `get_search_path`.

Fixes #330.
Fix CopySnapshot handler

This was previously crashing because the event interface was updated
to remove the operation object being sent as a kwarg.  This commit
adds this back.

To ensure we don't regress on this again, I've added an integration
test that actually copies a snapshot (encrypted and not encrypted).
This will ensure that this functionality will not be lost despite
any changes we might make to handler interfaces.
Merge branch 'fix-ebs-copysnapshot' into develop

* fix-ebs-copysnapshot:
  Fix CopySnapshot handler
  Handle case where only type key is defined in waiters
Fix test bug for py26
Fix insert_before in CredentialResolver

This method was not updated to use the same interface
as insert_after.  Now both methods are working as expected.
Added a unit tests for insert_before, as it look like there
previously was not one.
Merge branch 'fix-insert-before' into develop

* fix-insert-before:
  Fix insert_before in CredentialResolver
Merge branch 'fix-loaders' into develop

* fix-loaders:
  Search for files in order of get_search_paths()
Update several service models

Service updates include redshift, storage gateway, iam, sts, cognito-identity,
route53domains, and ec2.
Bumping version to 0.67.0
Merge branch 'release-0.67.0'

* release-0.67.0:
  Bumping version to 0.67.0
  Update several service models
  Fix insert_before in CredentialResolver
  Fix test bug for py26
  Fix CopySnapshot handler
  Search for files in order of get_search_paths()
  Handle case where only type key is defined in waiters
  Update retryhandler to handle change in error response structures