make Plot::default() behave like Plot::new()

Closes #380

Signed-off-by: Andrei Gherghescu <8067229+andrei-ng@users.noreply.github.com>

Author: andrei-ng

plotly/src/plot.rs

@@ -156,7 +156,7 @@ impl Traces {
 ///     Ok(())
 /// }
 /// ```
-#[derive(Default, Serialize, Clone)]
+#[derive(Serialize, Clone)]
 pub struct Plot {
     #[serde(rename = "data")]
     traces: Traces,
@@ -169,6 +169,12 @@ pub struct Plot {
     js_scripts: String,
 }
 
+impl Default for Plot {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl Plot {
     /// Create a new `Plot`.
     pub fn new() -> Plot {