Resample docstring default values changed

This docstring seems better, since TimeGrouper specifies it [that way][1] too:

[1]: https://github.com/pydata/pandas/blob/master/pandas/tseries/resample.py#L27

Author: metakermit

pandas/core/generic.py

@@ -231,9 +231,9 @@ def resample(self, rule, how=None, axis=0, fill_method=None,
               downsampling
         axis : int, optional, default 0
         fill_method : string, fill_method for upsampling, default None
-        closed : {'right', 'left'}, default None
+        closed : {'right', 'left'}, default 'left'
             Which side of bin interval is closed
-        label : {'right', 'left'}, default None
+        label : {'right', 'left'}, default 'left'
             Which bin edge label to label bucket with
         convention : {'start', 'end', 's', 'e'}
         kind: "period"/"timestamp"