Serve documentation from docs.geotrellis.io

[tnation14]

This PR makes the GeoTrellis documentation accessible from https://docs.geotrellis.io by adding an nginx container that reverse-proxies requests to https://geotrellis.readthedocs.io. I followed the method outlined at http://docs.readthedocs.io/en/latest/alternate_domains.html#cname-ssl.

Notable changes

• Add gtdocs-nginx container that reverse proxies all requests to readthedocs
• Add ECS service for gtdocs-nginx
• Add firewall rules to allow HTTPS ingress/egrees to the ALB and all traffic between the ALB and container instance.
• Add a Route53 record for docs.geotrellis.io

Testing

• see https://docs.geotrellis.io

• Run scripts/infra plan, ensure no changes are necessary.

  TRAVIS_COMMIT=dafb2db GT_SITE_SETTINGS_BUCKET=geotrellis-site-production-config-us-east-1 ./scripts/infra plan

Fixes #72

[hectcastro]

Ah, I was unaware of this tactic and figured you were just going to associate the subdomain with the DNS record.

Have you tried manually configuring a CloudFront distribution to mimic this reverse proxy pattern (using https://geotrellis.readthedocs.io as the origin with custom headers)? Seem like it could be possible and might allow us to avoid deploying a second instance of Nginx.

[tnation14]

Updated