Added plotting section to the user guide

Author: jbednar

docs/source/index.rst

@@ -116,3 +116,4 @@ data streaming systems like `Apache Flink <https://flink.apache.org/>`_,
    api.rst
    collections-api.rst
    async.rst
+   plotting.rst

docs/source/plotting.rst

@@ -0,0 +1,37 @@
+Visualizing streamz
+===================
+
+A variety of tools are available to help you understand, debug, visualize your streaming objects:
+
+- Most Streamz objects automatically display themselves in Jupyter notebooks, periodically updating their visual representation as text or tables by registering events with the Tornado IOLoop used by Jupyter
+- The network graph underlying a stream can be visualized using `dot` to render a PNG using `Stream.visualize(filename)`
+- Streaming data can be visualized using the optional separate packages hvPlot, HoloViews, and Panel (see below)
+
+
+hvplot.streamz
+--------------
+
+hvPlot is a separate plotting library providing Bokeh-based plots for Pandas dataframes and a variety of other object types, including streamz DataFrame and Series objects. 
+
+See `hvplot.holoviz.org <https://hvplot.holoviz.org>`_ for instructions on how to install hvplot.  Once it is installed, you can use the Pandas .plot() API to get a dynamically updating plot in Jupyter or in Bokeh/Panel Server:
+
+.. code-block:: python
+
+   import hvplot.streamz
+   from streamz.dataframe import Random
+   
+   df = Random()
+   df.hvplot(backlog=100)
+
+See the `streaming section <https://hvplot.holoviz.org/user_guide/Streaming.html>`_ of the hvPlot user guide for more details, and the
+`dataframes.ipynb` example that comes with streamz for a simple runnable example.
+
+
+HoloViews
+---------
+hvPlot is built on HoloViews, and you can also use HoloViews directly if you want more control over events and how they are processed.  See the `HoloViews user guide <http://holoviews.org/user_guide/Streaming_Data.html>`_ for more details.
+
+
+Panel
+-----
+Panel is a general purpose dashboard and app framework, supporting a wide variety of displayable objects as "Panes". Panel provides a `streamz Pane <https://panel.holoviz.org/reference/panes/Streamz.html>`_ for rendering arbitrary streamz objects, and streamz DataFrames are handled by the Panel `DataFrame Pane <https://panel.holoviz.org/reference/panes/DataFrame.html>`_.