Remove default value for ssl_certificate_arn

[tnation14]

Overview

This PR removes the default value for ssl_certificate_arn (which is now outdated) from variables.tf, and updates scripts/infra to use a .tfvars file to make it easier to override other defaults in the future.

Changes

• Remove default value for ssl_certficate_arn
• Set CloudWatch log retention policy to 30 days
• Updated scripts/infra to use a .tfvars file.
• Add docker-compose.ci.yml for local deployments.
• Add a memoryReservation to the ECS task definition to match the Task Definition currently running in Production.
• Add Deployment README.

Fixes #49

Testing

• Run scripts/infra according to the instructions in the new deployment README, ensure no changes are necessary.

  $ export GT_CHATTA_SETTINGS_BUCKET=geotrellis-site-production-config-us-east-1
  $ export AWS_PROFILE=geotrellis
  $ export TRAVIS_COMMIT=$(git rev-parse --short master)
  $ docker-compose -f docker-compose.ci.yml run --rm terraform ./scripts/infra plan

• Visit https://chatta.geotrellis.io. Ensure that the certificate serial number matches the serial number from the ACM console: https://console.aws.amazon.com/acm/home?region=us-east-1#/?id=4704eab3-c3f9-47fc-9568-a70a0038cf60.

  

[tnation14]

Updated to remove memoryReservation from ECS task definition and deployment tests.