Feature rollup (#129)

* Create a directory for the `future::server` module, which has become quite large. server.rs => server/mod.rs. Server submodules for shutdown and connection logic are added.

* Add fn thread_pool(...) to sync::server::Options

* Configure idle threads to expire after one minute

* Add tarpc::util::lazy for lazily executing functions. Similar to `futures::lazy` but useful in different circumstances. Specifically, `futures::lazy` typically requires a closure, whereas `util::lazy` kind of deconstructs a closure into its function and args.

* Remove some unstable features, and `cfg(plugin)` only in tests. Features `unboxed_closures` and `fn_traits` are removed by replacing manual Fn impls with Stream impls. This actually leads to slightly more performant code, as well, because some `Rc`s could be removed.

* Fix tokio deprecation warnings. Update to use tokio-io in lieu of deprecated tokio-core items. impl AsyncRead's optional `unsafe fn prepare_uninitialized_buffer` for huge perf wins

* Add debug impls to all public items and add `deny(missing_debug_implementations)` to the crate.

* Bump tokio core version.

src/tls.rs

@@ -1,6 +1,7 @@
 /// TLS-specific functionality for clients.
 pub mod client {
     use native_tls::{Error, TlsConnector};
+    use std::fmt;
 
     /// TLS context for client
     pub struct Context {
@@ -35,5 +36,16 @@ pub mod client {
             }
         }
     }
+
+    impl fmt::Debug for Context {
+        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+            const TLS_CONNECTOR: &'static &'static str = &"TlsConnector { .. }";
+            f.debug_struct("Context")
+             .field("domain", &self.domain)
+             .field("tls_connector", TLS_CONNECTOR)
+             .finish()
+        }
+    }
+
 }