Update docstring

silo.py

@@ -17,12 +17,13 @@ def pointdata(variables,
     Args:
         variables: list of variable code strings (see variable info below)
         api_key:   SILO api key
-        start:     start date (yyyymmdd)
-        finish:    finish date (yyyymmdd)
+        start:     start date (yyyymmdd, earliest date is '18890101')
+        finish:    finish date (yyyymmdd, latest date is yesterday)
         station:   weather station ID (or use 'lat' and 'lon')
         lat:       latitude (between -44° and -10°, in increments of 0.05°)
         lon:       longitude (between 112° and 154°, in increments of 0.05°)
         units:     include units in dataframe column names
+        output:    name of file to export data (csv format)
 
     Returns:
         Dataframe containing climate data time series