ENH: add fill_value to resample as per GH3715

Author: nchmura4

pandas/core/generic.py

@@ -4129,7 +4129,7 @@ def between_time(self, start_time, end_time, include_start=True,
 
     def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
                  label=None, convention='start', kind=None, loffset=None,
-                 limit=None, base=0, on=None, level=None):
+                 limit=None, base=0, on=None, level=None, fill_value=None):
         """
         Convenience method for frequency conversion and resampling of time
         series.  Object must have a datetime-like index (DatetimeIndex,
@@ -4164,6 +4164,11 @@ def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
 
             .. versionadded:: 0.19.0
 
+        fill_value: scalar, optional
+            Value to use for missing values, applied before resampling
+
+            .. version added:: 0.19.2
+
         To learn more about the offset strings, please see `this link
         <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
 
@@ -4268,6 +4273,10 @@ def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
         from pandas.tseries.resample import (resample,
                                              _maybe_process_deprecations)
         axis = self._get_axis_number(axis)
+
+        if(fill_value is not None):
+            self = self.fillna(fill_value)
+
         r = resample(self, freq=rule, label=label, closed=closed,
                      axis=axis, kind=kind, loffset=loffset,
                      convention=convention,