Update RealtimeDataFactory to use geomag-edge-ws
Currently using the legacy earthworm based web service at http://geomag.usgs.gov/map/observatories_data.json.php
Should be updated to use the new service at http://geomag.usgs.gov/ws/edge/
Should only affect the following classes (and related tests): https://github.com/usgs/geomag-web-absolutes/blob/master/src/htdocs/js/geomag/RealtimeDataFactory.js https://github.com/usgs/geomag-web-absolutes/blob/master/src/htdocs/js/geomag/RealtimeData.js