http2 compat tests

[ronag]

Maybe we should have some tests against http2 compat? Also, I think some optimizations can be performed for the http2 case.

[dougwilson]

Yea, now that there are some Node.js releases with http2 flagged, seems like a good time to start. There are four main items that we probably want to detect finished state for I think:

1. Request
2. Response
3. The stream
4. The overall session

I will take a look and dig in soon :)

[bjohansebas]

Now that this package is being modernized and on-finished is no longer an issue, I'm going to continue with the branch I had locally for HTTP/2

[Phillip9587]

Hey @bjohansebas do you have working tests for http2? Have you started some work?

[GroophyLifefor]

I did some work for implementing and testing http2, PR: #100