Remove usage of deprecated std::error::Error methods (#1206) (#1245)

tokio-timer/src/error.rs

@@ -58,20 +58,15 @@ impl Error {
     }
 }
 
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        use self::Kind::*;
-
-        match self.0 {
-            Shutdown => "timer is shutdown",
-            AtCapacity => "timer is at capacity and cannot create a new entry",
-        }
-    }
-}
+impl error::Error for Error {}
 
 impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        use std::error::Error;
-        self.description().fmt(fmt)
+        use self::Kind::*;
+        let descr = match self.0 {
+            Shutdown => "timer is shutdown",
+            AtCapacity => "timer is at capacity and cannot create a new entry",
+        };
+        write!(fmt, "{}", descr)
     }
 }