Percent snow units

[scotthavens]

The units for percent_snow should be fraction and not %. Propose to change the long_name as well to be more descriptive.

'percent_snow': {
            'units': 'fraction',
            'standard_name': 'percent_snow',
            'long_name': 'Fraction of precipitation as snow between 0.0 and 1.0'  
}

Long term, may be better to change percent_snow to snowfall_fraction as that is really what it is.

smrf/smrf/distribute/precipitation.py

Line 71 in 465d42c

'units': '%',