Address the following suggestions from @yanshuotan in issue #132:

• Return the .Rmd file used in create_docs() to allow user to directly edit this .Rmd
• Create a barebones option for the documentation file (e.g., return a raw markdown file with pointers to .png files for the visualizers and slots for the simulation documentation). This would be an alternative if the .html version is too big.
• Consider adding wrapper function or convenient way to automatically save visualizer plots to .png/.jpg