Define jquery in require.js config

[alimanfoo]

I was trying to view a notebook that used a javascript library (jstree) that had a dependency on jquery. When I load jstree via require, it goes looking for jquery, but because jquery is not defined in the require config, require tries (and fails) to load jquery from the wrong URL. I can work around this by manually calling require.config to define jquery, but it would seem better if nbviewer set this config with the correct URL from where jquery is already being loaded. Here's an example notebook illustrating the use case and workaround.

[parente]

nbviewer pulls in JS assets from jupyter/notebook, but does not configure the jquery URL like the notebook page template does (https://github.com/jupyter/notebook/blob/fcf5f39606aa7d5810c53f20b7f6694d025f9259/notebook/templates/page.html#L37). Seems reasonable that it might configure require to point to the bundled jquery too (https://github.com/jupyter/nbviewer/blob/master/nbviewer/templates/layout.html#L77)