TRAITS: Move summary trait to separate file

traits/src/main.rs

@@ -1,10 +1,5 @@
-pub trait Summary {
+mod summary;
-    fn summarize_author(&self) -> String;
+use summary::Summary;
-
-    fn summarize(&self) -> String {
-        format!("(Read more from {}...)", self.summarize_author())
-    }
-}
 
 pub struct NewsArticle {
     pub headline: String,

traits/src/summary.rs

@@ -0,0 +1,7 @@
+pub trait Summary {
+    fn summarize_author(&self) -> String;
+
+    fn summarize(&self) -> String {
+        format!("(Read more from {}...)", self.summarize_author())
+    }
+}