Enable region specific stacks

[kshinn]

Given that AWS is enabling and defaulting to region specific stacks, there is an option missing to specify which region we want the tool to send the AWS commands to.

For example, I have the following regionless stacks:

Stack A
Stack B

And the following Regional stacks in us-west-1:

Stack C
Stack D

When I run the tool, only Stack A and Stack B are available.

Please add an option where a user can specify a specific region.