Add feature for "due"
Feature to show todays date in output
Introduce due attribute on Todo
introduce on_date filter on todolist
introduce before_date filter
Introduce due-feature.
Brighten the headers.
Merge branch 'feature/due' into develop

* feature/due:
  Brighten the headers.
  Introduce due-feature.
  introduce before_date filter
  introduce on_date filter on todolist
  Introduce due attribute on Todo
  Feature to show todays date in output
  Add feature for "due"