short-hand default via derive

bip/src/bp.rs

@@ -78,17 +78,12 @@ impl Op {
     }
 }
 
+#[derive(Default)]
 pub struct Writer {
     data: HashMap<String, Vec<String>>,
     buf: Vec<u8>,
 }
 
-impl Default for Writer {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl Writer {
     pub fn new() -> Self {
         Self {