Fix display of list

src/schala_lang/parser.rs

@@ -95,8 +95,12 @@ impl fmt::Display for Expression {
             }
             ListLiteral(ref items) => {
                 write!(f, "[ ");
-                for item in items {
+                let mut iter = items.iter().peekable();
-                    write!(f, ", {}", item);
+                while let Some(item) = iter.next() {
+                    write!(f, "{}", item);
+                    if let Some(_) = iter.peek() {
+                        write!(f, ", ");
+                    }
                 }
                 write!(f, " ]")
             }