Make Cloudfront auth more configurable

[Vad1mo]

trafficstars

For continuous delivery reasons and improved security it would be better the secrets and other variables could be externalized.

The variables could be passed in as environment variables for example.

[payton]

This is an important point to bring up. Externalizing would be a good addition to the project.

Unfortunately, Lambda@Edge has some limitations in that it does not support environment variables. With that said, the next best thing may be to support AWS Parameter Store. This will require a bit more conversation on how to best implement it into the build process. Always open to suggestions on implementation and externalization methods.

[pldimitrov]

#38