$ npm i
$ npm start# date will be today if omitted
GET /api/tasks
GET /api/tasks?date=2016-1-1
GET /api/tasks?user=someone&date=2016-1-1
GET /api/tasks?user=someone&date=lastDay
# one user can only post once per day
POST /api/tasks {user: 'someone', content: 'anything as a string'}