Fix exercise generation

Author: AaronO

lib/retro.js

@@ -30,13 +30,13 @@ function exerciseBlock(exercise) {
     '{% exercise %}',
     render(exercise.content),
     '{% initial %}',
-    exercise.initial,
+    exercise.code.initial,
     '{% solution %}',
-    exercise.solution,
+    exercise.code.solution,
     '{% validation %}',
-    exercise.validation,
+    exercise.code.validation,
     '{% context %}',
-    exerciseObj.context,
+    exercise.code.context,
     '{% endexercise %}',
     ].join('\n');
 }