Placeholder column to mark done/not done
Marks done tasks as struck out. Fixes tests.
Troubleshooting.
Added undo keyword. Deleted event filter.
Fixed text-edit line issue. Updated exception handler.
Fixed lints, removed timer.
Fixes #249.
Fixes #237
Fixes #236.
Test fixes.
Merge pull request #270 from angathorion/mark-done

Marks done tests by strike-outs; test fixed