Add JS for simulation, tooltip, and halo (#30)

* add JS for simulation, halo, and tooltip

relates to #29

* correcting previous commit

* code cleanup

* code review changes

this commit reflects changes requested upon code review from @decentralion: variable declaration, using => for functions, removing unneccessary comments, and some other substantive changes. I also changed naming conventions from 'd3' to just the function name since I don't need to identify d3 DOM manipulation functions anymore. I also changed 'if' statements to switch calls for easier reading.

* remove unhelpful comments

* remove 'rMorton' folder from this repo

Author: Ryan Morton