Feature: look up snapshot ids by region from chef config data.

Squashed commit of the following:

commit 960d7abba089d9046bf567b434ed126bd66221c3
Author: Chris Howe <howech@infochimps.com>
Date:   Wed May 28 17:01:59 2014 -0500

    When building a machine, lookup the snapshot name in chef config data so that we can associate a different snapshot with each name by region.

    Change-Id: Id12fcff2e9c1b3d88e571a47b5454c3b3cbd0ed5

commit 2b1ed75634ab6c134c73ea287147e293c97a7f70
Author: Chris Howe <howech@infochimps.com>
Date:   Wed May 28 17:01:03 2014 -0500

    Added an error message to the "mismatched regions" error that allows you to know which setting is wrong.

    Change-Id: I681ef1e59984798bc95acce2f8a4940c2236dffe

commit ca0afc982125ba5aa30fec0c3f459aae195f0ca0
Author: Chris Howe <howech@infochimps.com>
Date:   Wed May 28 17:00:33 2014 -0500

    removed crufty VOLUME_IDS lookup for snashot_id

    Change-Id: I01621d6d94bc3d373e333e0e134b8a12100a6a9c

Change-Id: I1a4d6e91c3d5ce81dc359490b02711bed8291ae1