view_article.html:
- show the selected node title, and make the selected node more repulsive to see the arrow markers and links better
- selection is based on mouseover
- hover text element should probably be a div html element and not an svg element, since the svg text element doesn't do text wrapping...I'd have to calculate the length :(

models.py:
- extra check for avoiding a PubMed request for an empty list of articles

custom.css:
- add a border around the graph so I can at least tell when the scroll wheel will zoom the graph or scroll the page