feat(server): change default dispatcher

- Deprecates the `no_proto` configuration on `Server`. It is always
  enabled.
- Deprecates all pieces related to tokio-proto.
- Makes the tokio-proto crate optional, and the `server-proto` feature
  can be used to completely remove the dependency. It is enabled by
  default.

Cargo.toml

@@ -32,7 +32,7 @@ percent-encoding = "1.0"
 relay = "0.1"
 time = "0.1"
 tokio-core = "0.1.6"
-tokio-proto = "0.1"
+tokio-proto = { version = "0.1", optional = true }
 tokio-service = "0.1"
 tokio-io = "0.1"
 unicase = "2.0"
@@ -48,4 +48,4 @@ default = ["server-proto"]
 nightly = []
 raw_status = []
 compat = [ "http" ]
-server-proto = []
+server-proto = ["tokio-proto"]