Compression v2

[bjohansebas]

I’m opening this issue to complete the backlog for this new major version.

Pending tasks:

• support res.removeListener('drain'), res.once('drain') #153 (Need reviews)
• new way to pass the configuration to the encodings #232 (Need reviews)
• fix: call underlying implementation properly #183 (Need help for finish the work)
• Support for Node.js 8 native http2 #122
  • on-headers v2 jshttp/on-headers#18, with explicit support for HTTP/2
  • Release Proposal: on-finished@3.0.0 jshttp/on-finished#57, Mainly, the HTTP/2 support in the isFinished function
  • support http2 #211
• Weaken outgoing ETags #45

A beta version will be released after #153 and #232 are merged.