Web UI should provide a checkbox that will include or when unchecked, exclude all closed tasks from display and save command

[bicarbon8]

The current index.html has a (currently hidden) checkbox with id of "showClosed-checkbox" that should be bound to javascript events inducing the displaying of and filtering out of closed tasks based on the state of the checkbox.

REPRO:

1. open index.html and see the checkbox with id of "showClosed-checkbox"
2. open js/todoTxt.js and see the TODO: calling out filtering out of closed items (inside of "processTasksFromLocalStorage")

ACTUAL:
the checkbox is hidden and has no functionality

EXPECTED:
the checkbox, when unchecked will update the UI to display only the active (not closed) list of tasks and when checked will display the active and closed list of tasks. Additionally, when unchecked, no closed tasks will be saved to the output file when saving to a local machine

[bicarbon8]

fixed in 1b442be