Keep track of region in config file

[richford]

Presently, the user could create a few VPCs, switch regions, create a few more, then be unable to retrieve the old region's VPCs.

[richford]

Proposed solution: format the config file with sections like

[region-name resource-type]

e.g.

[us-east-1 roles]
[us-west-1 security-groups]

For collections of resources, such as PARS and knots, use region as an option name, e.g.

[pars pars-name]
region = region-name
role = role-name
etc.

[richford]

Each resource object should have a region parameter and check that it matches get_region before doing method stuff