Feature: Support custom Bokeh resource loading

[canavandl]

Uncomment only one, leave it on its own line:

type: bug

type: feature

It would be nice to allow users to specify their own Bokeh resource loading. I believe it would be possible to implement this by having the import chartify invocation defer to a previous call to bokeh.io.output_notebook.

This would enable users to:

• keep notebook sizes small by loading BokehJS from the CDN (or other locations) and not inlining it
• load only the required resources (ie not loading bokeh-widgets.min.js if it's not needed)

This would almost make chartify work in different notebook contexts, by letting users specify
output_notebook(notebook_type='zeppelin')

Example code:

# user specifies their own bokeh/notebook configuration
from bokeh.io import output_notebook
output_notebook()

# load chartify package into namespace but defer to above bokeh.io.output_notebook call
import chartify