Update to use version 3 of the Amazon Echo skill API

[dbudwin]

Description

Update to use version 3 of the Alexa Smart Home Skill API per issue #106.

Motivation and Context

This will improve upon the features we can offer via RoboHome and also prepare the RoboHome project in the event that Amazon deprecates version 2.

How Has This Been Tested?

All the tests pass and many of the existing tests were modified to accommodate changes to the API between version 2 and 3. I also used Postman to manually hit the RoboHome API to verify the response I was getting would be a valid response to send to Amazon based on their documentation of what sample requests and responses look like. There is also a pull request that will be opened shortly for the RoboHome-Echo project where I could use an NPM package called lambda-local to test the RoboHome API by making requests via my Smart Home lambda.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement/Security (non-breaking change which is not noticeable to end users)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I created a feature branch and did not open a pull request from my master branch.
• My code follows the code style of this project.
• My change requires an update to the README and I have updated it accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• This is a complete change and doesn't leave the project in a bad state.
• All new and existing tests pass.