Update Si1000.py

updated from issue reported to tridge original branch
tridge#5

Humidity was not reporting until I changed 'humidity' to 'outHumidity' in Si1000.py driver. Now it's working.  Credit goes to github user: bhpost

weewx/Si1000.py

@@ -64,7 +64,7 @@ def __init__(self, **stn_dict):
             'wind_direction_degrees' : ('windDir',   self.adjust_wind_direction),
             'wind_speed_mph'         : ('windSpeed', None),
             'temperature_F'          : ('outTemp',   None),
-            'humidity_pct'           : ('humidity',  None),
+            'humidity_pct'           : ('outHumidity',  None),
             'rain_spoons'            : ('rain',      self.convert_rain)
             }