Fixed bug in anonymisation function

The function `do_anonymous` in `hektor.py` was dependant upon the iteration order of a dictionary being the same as the insertion order. This is an implementation detail of CPython3.6 and should not be relied upon.

hektor.py

@@ -227,11 +227,11 @@ def do_anonymous(students: Dict[str, Union[str, List]]):
     reverser = {get_random_xkcd_identifier(): s for s in students}
     students_anonymous = [{
         'fullname': ' '.join(w[0].capitalize() + w[1:]
-                             for w in r.split(DELIMITER)),
-        'identifier': r,
-        'username': r,
+                             for w in pseudo_identifier.split(DELIMITER)),
+        'identifier': pseudo_identifier,
+        'username': pseudo_identifier,
         'submissions': student['submissions']
-    } for r, student in zip(reverser, students)]
+    } for pseudo_identifier, student in reverser.items()]
 
     with open(args.personal_secret_table, 'w') as out:
         print('key;previous identifier;fullname', file=out)