data exporting support, supports exporting task history via csv

* adds the following new dependencies: 
** moment
** express-csv
* recommend replacing functionality of 'relative-date' with features from 'moment'
* adds new routes for data export
* supports retrieval of CSV history via the API and in browser
** /api/v1/export/history (requires typical API authorization)
** /export/history.csv (requires session authorization)