Fix table column converters for astropy versions >= 4.1
Created by: darafferty
This PR fixes the column converters as needed for the change to astropy.table.Table.read() in v4.1. It also fixes some comparisons to get rid of warnings.
Created by: darafferty
This PR fixes the column converters as needed for the change to astropy.table.Table.read() in v4.1. It also fixes some comparisons to get rid of warnings.