Rename global plotly library object in JavaScript

The global plotly library object was renamed from 'Plotly' to '_Plotly'
in plotly.py 3.4.0 to avoid a naming conflict when a Jupyter Notebook
heading contained the text 'Plotly'

See:
plotly/plotly.py#816
plotly/plotly.py#1250

Author: jonmmease

Diff for: holoviews/plotting/plotly/plotlywidgets.js

@@ -32,8 +32,8 @@ var PlotlyMethods = {
         plot.data[i][key] = data.data[i][key];
       }
     }
-    Plotly.relayout(plot, data.layout);
-    Plotly.redraw(plot);
+    _Plotly.relayout(plot, data.layout);
+    _Plotly.redraw(plot);
   }
 }
 

Diff for: holoviews/plotting/plotly/renderer.py

@@ -19,8 +19,8 @@
     plot.data[i][key] = obj[key];
   }});
 }});
-Plotly.relayout(plot, data.layout);
-Plotly.redraw(plot);
+_Plotly.relayout(plot, data.layout);
+_Plotly.redraw(plot);
 """
 
 PLOTLY_WARNING = """
@@ -98,7 +98,7 @@ def _figure_data(self, plot, fmt=None, divuuid=None, comm=True, as_script=False,
                       '</script>')
 
         script = '\n'.join([
-            'Plotly.plot("{id}", {data}, {layout}, {config}).then(function() {{',
+            '_Plotly.plot("{id}", {data}, {layout}, {config}).then(function() {{',
             '    var elem = document.getElementById("{id}.loading"); elem.parentNode.removeChild(elem);',
             '}})']).format(id=divuuid,
                            data=jdata,