Support CloudEvent as triggers in Functions Frameworks

[anguillanneuf]

See #23 (comment)

@frankie567

[di]

If I'm understanding correctly, this is already supported (added in #56) -- or am I missing something?

[anguillanneuf]

Ohh, you are right.

I think the issue should be to update the Pub/Sub quickstart to use (event, context):

https://github.com/GoogleCloudPlatform/functions-framework-python#quickstart-pubsub-emulator

Hm, but that is not feasible because the Pub/Sub emulator does not send messages formatted in CloudEvent and we can't change that. Okay to close if no user comment.

[di]

I'll close this and reopen #23.