Remove default 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This PR removes the default value for ssl_certificate_arn (which is now outdated) from variables.tf, and updates scripts/infra to use a .tfvars file to make it easier to override other defaults in the future.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
• Updated scripts/infra to use a .tfvars file.
• Add docker-compose.ci.yml for local deployments.

Fixes #82

Testing

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

  $ export GT_SITE_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

[hectcastro]

The build is currently failing. Looks like the static Dockerfile is referencing a node package, but now it should be nodejs.

[tnation14]

Fixed. I was also able to take care of the jai_core resolution failure by adding it to SBT librarayDependencies with an explicit URL.

[hectcastro]

If you are confident that fixed it, then consider closing https://github.com/geotrellis/geotrellis-site/issues/79 too.