Page rendering is slow (does not properly render until JSMol is loaded)

[giovannipizzi]

Probably we should make sure the JSmol rendering is delayed (maybe it's enough to move this into the onload method?)

EDIT: I checked, it's not as trivial - moving the loading of JSMol in the onload function does not work (the widget does not appear and there is a mysterious JQuery error in the console).

(Moved from materialscloud-org/seekpath#63)