Set proper timestamps in residual calculated absolutes
Merged
requested to merge ghsc/users/erigler/geomag-algorithms:fix-residual-absolutes-timestamp-assignment into master
Maintenance scheduled for Thursday, April 10, from 5 PM to 6 PM ET.
Fixes #75 (closed)
When geomagio.residual.calculate() is called with adjust_reference set equal to True, the start/end timestamps now both reflect the time of the first absolute measurement (i.e., West Down). This is consistent with the residual absolute spreadsheet calculations.