Upload Jenna's final presentation and accompanying files

1.  Added folders for ex1-ex3
2.  Added revised presentation
3.  Only included code files + html files (for viewing only).  Other files (e.g. .md) should not be modified, so I did not include them.

I couldn't figure out how to merge my .Rpres file with yours, so if you have a better way of doing it, please feel free!