Mention that installing `pandoc`, `make`, and `graphviz` might be necessary for doc builds (#1584)
Mention that installing `pandoc`, `make`, and `graphviz` might be necessary for doc builds (#1584)

* Mention pandoc install as prereq for doc build

* Mention installation of graphviz

* Update installation requirements for doc builds

* Update installation requirements for doc builds

* Update installation instructions

* Use common link for make
StanczakDominik/PlasmaPy