Problem: Expected text for interactive marks is in a separate json file
from the tutor file. When the tutor file is updated, line numbers
(potentially many) have to be updated in the json file. This is a
burden for maintenance and automatic testing.
Solution: Put the expected text inline in the tutor file, marked
with `[[]]`. Parse and remove the comments before opening the tutor
file so extmarks can be applied.
dbdd73e846
