Minor change rollup

* Head off imminent breakage due to https://github.com/rust-lang/rust/pull/51285.
* Fix examples and documentation to use a recently-gated feature, `proc_macro_path_invoc`.
* Update dependency versions.

examples/sync_server_calling_server.rs

@@ -3,7 +3,7 @@
 // Licensed under the MIT License, <LICENSE or http://opensource.org/licenses/MIT>.
 // This file may not be copied, modified, or distributed except according to those terms.
 
-#![feature(plugin, use_extern_macros)]
+#![feature(plugin, use_extern_macros, proc_macro_path_invoc)]
 #![plugin(tarpc_plugins)]
 
 extern crate env_logger;