Enable connect_to_region('us-gov-west-1') for all services in GovCloud

added region information to the __init__.py for each service

additional updates supporting govcloud functionality:
- update auth.py HmacAuthV4Handler to return the correct region name
- update iam/connection.py to return the correct IAM signin url for govcloud
add unit test coverage for HmacAuthV4Handler.credential_scope()

validate two existing use cases with iam.amazonaws.com and
iam.us-gov.amazonaws.com as well as the potential use case of
iam.<some-region>.amazonaws.com with the non-existant
iam.us-west-1.amazonaws.com
Add db_subnet_group to restore_dbinstance_from_point_in_time
Enable connect_to_region(us-gov-west-1) for vpc services in GovCloud
Bugfix: s/LastUpdatedTimestamp/LastUpdatedTime

The cloudformation api is returning xml that does not have
LastUpdatedTimestamp elements, but rather LastUpdatedTime elements. Here
is an example:

<ListStacksResponse xmlns="http://cloudformation.amazonaws.com/doc/2010-05-15/">
  <ListStacksResult>
    <StackSummaries>

...snip

      <member>
      <StackId>STACKY_DOO_DAH</StackId>
      <StackStatus>UPDATE_COMPLETE</StackStatus>
==>   <LastUpdatedTime>2013-08-09T18:58:22Z</LastUpdatedTime>
      <StackName>StackyDooDah</StackName>
      <CreationTime>2013-08-09T15:18:49Z</CreationTime>
      <TemplateDescription>juggernauts</TemplateDescription>
      <StackStatusReason/>
      </member>

This commit fixes this and adjusts a couple of tests accordingly.
updated the connection to use boto.dynamodb2.connect_to_region
Conflicts:
	docs/source/dynamodb2_tut.rst
Merge remote-tracking branch 'carllen/connect_to_region_us-gov-west-1' into develop
Fixed STS' ``assume_role_with_web_identity`` method.
Correctly fetch VPC instances from SG.

Use filters to fetch the instances.
Conform to PEP8, except E501
Fixed a typo in DDBv2's create docstring.
Further fixed STS ``assume_role_with_web_identity``.
Add unit tests for new security group filtering behavior
Added a fix for ``request_id`` not being present.
make ResourceRecordSet work when iterated through multiple times
test for ResourceRecordSet miscounting problem
PEP8 fixes
Merge pull request #1677 from danielgtaylor/vpc-secgroup

Update SecurityGroup instance fetching to use filters; Fixes VPC instance issue. Fixes #1677 #1665.
Fix typo and set record limit to minimum required to reproduce the issue.
Fix a bug where only 100 records can be added or deleted at a time by sending these batches and starting a new batch when crossing 100, 200, etc boundaries. Integration tests now pass.