Index.js can handle a promise returned by handler.js

[padiazg]

Proposed in isue #92

Description

The code at index.js calls handler and checks the type of the value returned, if it is a promise then resolves it and then calls the common callback.

How Has This Been Tested?

Build and deploy commenting and uncommenting the code in handler.js, to return either a final value or a promise. Check in Portal.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [ x I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.