JWS signatures. Re-read -07 and noted missing features.

Author: yaronf

README.md

@@ -5,7 +5,7 @@ This is a nearly feature-complete implementation of draft -07, including all tes
 ### Notes and Missing Features
 * The `Accept-Signature` header.
 * Inclusion of `Signature` and `Signature-Input` as trailers is optional and is not yet implemented.
-* Extracting specialty components from the "related request".
+* Extracting specialty components from the "related request". See [related issue](https://github.com/httpwg/http-extensions/issues/1905).
 * In responses, when using the "wrapped handler" feature, the `Content-Type` header is only signed if set explicitly by the server. This is different, but arguably more secure, than the normal `net.http` behavior.
 * Multiple Signatures (Sec. 4.3).
 * The `sf` parameter, and in particular behavior when it is *not* given.