defaultChecker reads the actual file contents instead of relying on diff
defaultChecker reads the actual file contents instead of relying on diff

Fixes having the solution and expected output lines mixed up when they're
"similar" whitespace-wise, and thus not considered as different.

France-ioi/taskgrader,France-ioi/taskgrader,France-ioi/taskgrader,France-ioi/taskgrader,France-ioi/taskgrader,France-ioi/taskgrader,France-ioi/taskgrader