Be able to opt-out the feature "hyper/tcp"

[kvinwang]

We are building web services targeting to wasm with hyper and a custom TcpStream. The feature "hyper/tcp" is a trouble because it would enable some dependencies doesn't compile when targeting to wasm.

error[E0583]: file not found for module `sys`
   --> /home/kvin/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.4/src/lib.rs:124:1
    |
124 | mod sys;
    | ^^^^^^^^
    |
    = help: to create the module `sys`, create file "/home/kvin/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.4/src/sys.rs" or "/home/kvin/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.4/src/sys/mod.rs"

error: Socket2 doesn't support the compile target
   --> /home/kvin/.cargo/registry/src/github.com-1ecc6299db9ec823/socket2-0.4.4/src/lib.rs:127:1
    |
127 | compile_error!("Socket2 doesn't support the compile target");

It would be good if routerify allow to opt-out the "hyper/tcp" (disable RouterService by a feature gate). Or better make the RouterService more generic, like let the user decide how to get the remote_addr?