WhyLabs callback

[jamie256]

Add a WhyLabs callback handler

• Adds a simple WhyLabsCallbackHandler
• Add required dependencies as optional
• protect against missing modules with imports
• Add docs/ecosystem basic example

based on initial prototype from @andrewelizondo

this integration gathers privacy preserving telemetry on text with whylogs and sends stastical profiles to WhyLabs platform to monitoring these metrics over time. For more information on what WhyLabs is see: https://whylabs.ai

After you run the notebook (if you have env variables set for the API Keys, org_id and dataset_id) you get something like this in WhyLabs:

Who can review?

@agola11 @hwchase17