Add do_region, rename config.region -> aws_region.
Set 600 permissions recursively to all the secret/ submodule.
Pin cloudmaster to salt v.0.15.3.

Latest (actually, only) apt version will not authenticate minions
correctly, for some reason.
Actually enable ufw (!).
Add Digital Ocean configuration files.

Launching Digital Ocean lantern-peers is tested to work now,
although the cloudmaster is still configured to always launch AWS
instances.
Merge branch 'master' of github.com:getlantern/lantern_aws