moves addition of item to new AddItemActivity
WIP: adds 'set due date' button with date picker to edit and add activities, and makes keyboard have a done button instead of a return button for the edit and add activities"
WIP: can now set due date when adding new items
WIP: shows item due date on item activity if it is set
edit activity can now display and save new due date
changes item's due date from being sql Date type to being a util Date type
formats dates using the android date formatter
displays due date on todo list in main activity
refactors, and cleans up listview
cleanup and show edit/add titles in edit and add activities when it makes sense
greys out due dates before today (still allows user to select those dates) & removes a unecessary methods associated with hiding the soft keyboard
improves date display
adds long click listener to due date display on add and edit pages. long click to clear date
updates readme and gif