Subclassed to offset histogram by defined amount.

def _process_hist(self, hist):
        """
        Subclassed to offset histogram by defined amount.
        """
        edges, hvals, widths, lims, isdatetime = super(SideHistogramPlot, self)._process_hist(hist)
        offset = self.offset * lims[3]
        hvals *= 1-self.offset
        hvals += offset
        lims = lims[0:3] + (lims[3] + offset,)
        return edges, hvals, widths, lims, isdatetime