fix missing output files for user stories

[pamfilos]

For the PID showcase website we need the output files to display the user stories more complete

Some files like HTML output generated by the notebook are missing

e.g.

pidgraph-notebooks-python/user-story-2-software-citations/py-software-citations-with-output.ipynb

Line 322 in 5d8ffed

"IFrame(src=\"./out.html\", width=500, height=500)"

A good workaround is to have the output HTML (and the rest of the generated outputs ) in a base64 encoded format, so that it can be passed like so

<iframe src="data:text/html;base64,SFRNTCCFDCBJTiBBIElGUkFNRQ==" frameborder="0"></iframe>