Improve the walk up test to prove that DustJS is doing dynamic scoping, not lexical scoping.

src/renderer/renderer.rs

@@ -181,6 +181,7 @@ impl<'a> DustRenderer<'a> {
 fn walk_path<'a>(
     context: &'a dyn ContextElement,
     path: &Vec<&str>,
+    breadcrumbs: Vec<&'a dyn ContextElement>,
 ) -> Result<&'a dyn ContextElement, RenderError<'a>> {
     let mut output = context;