Support grpc-web

[jhump]

The representation of gRPC requests and message data on the wire in the httpgrpc package is quite different from that used to by grpc-web (which also aims to support gRPC on an HTTP 1.1 channel).

To converge on a compatible approach, the httpgrpc package should seamlessly support the same wire format details as grpc-web (possible "v2" of its wire format?). That will allow the server side to actually just use an existing grpc-web implementation for Go, and it also means the Go client could be used with other grpc-web server implementations.

Supporting this new format would also be an ideal time to address #20 (which requires a change to the on-the-wire representation of a gRPC request anyway).

[ChristianWeyer]

Do you have any timeline for this much-wanted feature @jhump ? Thanks :-)

[jhump]

@ChristianWeyer, I'm afraid there is no timeline at the moment. Sorry.