add vpc tags

[deoxxa]

This relies on the same things as #173 - namely mitchellh/goamz#77. With this, it becomes possible to tag VPC instances. Pretty straightforward.

[pearkes]

Same story as this. See #87

[serenitus]

Perhaps the config language has moved on?

From:http://www.terraform.io/docs/configuration/syntax.html

Maps can be made with the {} syntax: { "foo": "bar", "bar": "baz" }

[pearkes]

Hey @deoxxa! I'm going to close this as we added proper set support in #211. We definitely still need this, but I think that the first class support changes it a lot. Appreciate your help, sorry we couldn't get this merged in.