Add extra regions for SES

Since early this year, SES has been extended to `us-west` and `eu-west` regions ( http://docs.aws.amazon.com/ses/latest/DeveloperGuide/regions.html ).
Given that, it would be nice to have it as part of this `aws` library.

One note about this PR: it removes `sesUsEast` and makes it explicit which specific US region we want to use this in... so it breaks backwards compatibility for users who might be using `sesUsEast` directly. For that reason, it might be worth leaving `sesUsEast` which would then default to `sesUsEast1` ...?