Added professor johnson's files
Bahhh forgot to commit after some work
Added a pattern matching solution for diff'
Came up with an awesome guard and pattern matching solution for swapper'
Add comment to separate versions
Added a cool function to do take from the back of a list
Added a list_set' solution for non-infinite lists
Added an extra correct version of list_set''
Added a sweet filtering implimentation fo count_occurrences'