Roadmap 1.0

1. Respond multiple content-types per coproduct endpoint (see #575, #583, and #794)
2. finch-generic, a standalone package providing generic derivation (see #528)
3. JSON streaming request (see #336, #557, and #812)
4. Figure out whether or not to keep ValidationRule (see #513)
5. Better API for io.finch.items (see #529)
6. Decode JSON directly from Buf (see #511)
7. Better story for Encode.*[Exception] (see #547, Finch No Exceptions)
8. ADT representing Endpoints metadata (see #581)
9. Reduce the performance gap between Finagle/Finch to 5%