aacgm in develop branch now requires a year argument for aacgmConv*

Fixing aacgm module calls in coordUtils.py and requiring datetime argument when mag coordinates are requested.

Otherwise, looks good. Apply this patch and send in a merge request against mainline develop branch. You may want to adjust the tests assocaited with 'mag' coords now and update the expected values... 
large changes in  dateTime.year arguments should result in slightly different mag coord conversions now.