message: Fix for new Pandas API
diff: @@ -42,6 +42,7 @@ from markdown import markdown
  import numpy as np
  import pandas as pd
  from pandas.tseries.frequencies import to_offset
  +from pandas.tseries.offsets import DateOffset
  import polyline
  import simplejson as json
  @@ -1398,7 +1399,8 @@ class NVD3TimePivotViz(NVD3TimeSeriesViz):
  fd = self.form_data
  df = self.process_data(df)
  freq = to_offset(fd.get("freq"))
  - freq.normalize = True
  + freq = DateOffset(normalize=True, **freq.kwds)
  + df.index.name = None
  df[DTTM_ALIAS] = df.index.map(freq.rollback)
  df["ranked"] = df[DTTM_ALIAS].rank(method="dense", ascending=False) - 1
  df.ranked = df.ranked.map(int)
  