Fix grammar in core/nodes etc. (#608)

* Fix grammar

* Nothing we can *do* except ...

* Implementer

* Implementation

core/src/nodes/node.rs

@@ -25,7 +25,7 @@ use std::fmt;
 use std::io::Error as IoError;
 use std::sync::Arc;
 
-// Implementor notes
+// Implementation notes
 // =================
 //
 // In order to minimize the risk of bugs in higher-level code, we want to avoid as much as

muxers/mplex/src/lib.rs

@@ -164,7 +164,7 @@ pub struct Multiplex<C> {
 
 // Struct shared throughout the implementation.
 struct MultiplexInner<C> {
-    // Errored that happend earlier. Should poison any attempt to use this `MultiplexError`.
+    // Error that happened earlier. Should poison any attempt to use this `MultiplexError`.
     error: Result<(), IoError>,
     // Underlying stream.
     inner: executor::Spawn<Fuse<Framed<C, codec::Codec>>>,

transports/tcp/src/lib.rs

@@ -310,7 +310,7 @@ impl Stream for TcpListenStream {
                             .expect("generating a multiaddr from a socket addr never fails"),
                         Err(err) => {
                             // If we can't get the address of the newly-opened socket, there's
-                            // nothing we can except ignore this connection attempt.
+                            // nothing we can do except ignore this connection attempt.
                             error!("Ignored incoming because could't determine its \
                                     address: {:?}", err);
                             continue