calc_rad_loss(): changed delimiter when calling dropwhile() (forgot to do that
in a previous commit) and changed replaced usage of csv.DictReader with
csv.reader as chianti_rad_loss.csv currectly has no column headings unlike
temperature and emission measure data files and so csv.DictReader cannot be
used.
Changed delimiter from ';' to ' ' when calling csv.reader in calc_rad_loss().
(Forgot to do this in previous commit).
Imported sunpy.sun.sun and corrected syntax of obstime input and checking
output in example in docstring of goes_lx().