GitHub token env vars

[ashawley]

• Objective: Store GitHub token in encrypted environment variables in AWS
• Presently, GitHub token is stored in configuration file.
• Rationale: AWS encrypted variables are more secure and can be updated easier without a need for a new build to be uplaoded.
• Safety: If the variable isn't in the environment variable, then fail gracefully.
• Safety: If the variable isn't in the environment variable, try the config file?
• Configuration: Document use of AWS Lambda environment variables.
• Configuration: Document use of env locally for local development.

[ashawley]

http://docs.aws.amazon.com/lambda/latest/dg/env_variables.html