update default output to reflect current packer release

Updated the spot price docs

fixed `packer --version` to show version again

Fix broken links in the DigitalOcean documentation

atlas post-processor on 32bit uint32 overflows int

post-processor/atlas/util.go:16: constant 4294967295 overflows int
Signed-off-by: BlackEagle <ike.devolder@gmail.com>

atlas post-processor unknown atlas.UploadartifactOpts field BuildId

in https://github.com/hashicorp/atlas-go/blob/master/v1/artifact.go
we can see it is BuildID and not BuildId
Signed-off-by: BlackEagle <ike.devolder@gmail.com>

Resource pool defaults

builder/digitalocean: default to nyc3