Add some integration tests for the Alexa Lambda function

[dylano]

Looking into a couple of mocha-friendly libraries to help with Alexa testing:

• alexa-conversation
  • this one has some trouble with DynamoDB, complaining about AWS region when instantiating table: "Missing region in config"
  • there is some discussion here and a possible resolution by using a local version of Dynamo: https://github.com/alexa/alexa-skills-kit-sdk-for-nodejs/issues/134, https://github.com/alexa/alexa-skills-kit-sdk-for-nodejs/issues/139
• virtual-alexa
  • https://github.com/bespoken/virtual-alexa
  • haven't tried this one yet, not sure if we'll hit the same DynamoDB issue

[dylano]

Got far enough with virtual-alexa to verify that it runs into the same Dynamo region config issue. Shelving this for now.