for custom domains for regions other than us-east-1

[nzoschke]

#12 introduced a side effect where the cert has to be in us-east-1.

If the stack was created in us-west-2, etc. you get this error: Invalid certificate ARN: arn:aws:acm:us-west-2:572007530218:certificate/26e813b5-3a21-43e0-bbfc-ad02afa17cb0. Certificate must be in 'us-east-1'.

It looks like you can manually create the ACM cert in us-east-1 and assign it to an API Gateway in another region, but that defeats the automation.

We could still support us-west-2, etc, by adding a cert ARN parameter and the various conditional bits