bug in make/build website: "Unknown option --citeproc.", "gsed not found"

[cleong110]

Grouping these together, some minor issues when building.

#96 fixes both of these issues.

Colab notebook demonstrating: https://colab.research.google.com/drive/1eSxAr5HwlxUzmahRKQqqrQWhr3Oa2JZO#scrollTo=nAleRKVIHnBC