Updating JSON-RPC crates (#4934)

* New version of jsonrpc.

* Better invalid encoding messages

* Fixing deprecated methods of tokio_core

* Using dedicated branch for jsonrpc

* Bump

ethcore/src/spec/spec.rs

@@ -326,7 +326,7 @@ impl Spec {
 	pub fn load<R>(reader: R) -> Result<Self, String> where R: Read {
 		match ethjson::spec::Spec::load(reader) {
 			Ok(spec) => Ok(spec.into()),
-			_ => Err("Spec json is invalid".into()),
+			Err(e) => Err(format!("Spec json is invalid: {}", e)),
 		}
 	}