data export commit, supports exporting task history via csv
*adds the following new dependencies: moment, express-csv
*recommend replacing functionality of 'relative-date' with features from 'moment'
*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)
*adds new routes for data export
Merge branch 'develop' of https://github.com/snicker/habitrpg into develop