Structure for ordering, need to implement for serde_json::Value.

src/bin.rs

@@ -11,6 +11,7 @@ use renderer::RenderError;
 use renderer::Renderable;
 use renderer::WalkError;
 use renderer::Walkable;
+use std::cmp::Ordering;
 use std::env;
 use std::fs;
 use std::io::{self, Read};
@@ -158,4 +159,9 @@ impl CompareContextElement for serde_json::Value {
         }
         false
     }
+
+    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering> {
+        // TODO: Implement
+        None
+    }
 }