Fix rick.charts.line_chart's baseline param

[chmnata]

Got this error when trying to follow rick's rick's chart [sample ] (https://cityoftoronto.github.io/bdit_python_utilities/auto_examples/plot_line.html#sphx-glr-auto-examples-plot-line-py) using the baseline param

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-13-840157d7e7c5> in <module>
     24 total2=pandasql.read_sql(query, con)
     25 total2
---> 26 fig, ax, props = rick.charts.line_chart(total['count'], 'Trips', 'Time', baseline = total2['count'])

/etc/jupyterhub/.venv/src/rick/charts/rick.py in line_chart(data, ylab, xlab, **kwargs)
    276         fig, ax =plt.subplots()
    277         ax.plot(data ,linewidth=3, color = colour.purple)
--> 278         if baseline:
    279             ax.plot(baseline ,linewidth=3, color = colour.grey)
    280 

/etc/jupyterhub/.venv/lib/python3.5/site-packages/pandas/core/generic.py in __nonzero__(self)
   1476         raise ValueError("The truth value of a {0} is ambiguous. "
   1477                          "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
-> 1478                          .format(self.__class__.__name__))
   1479 
   1480     __bool__ = __nonzero__

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().