Add delete method
Revert "Add delete method"

This reverts commit 0692857c42872093cb368e97689b42c8b7a3b3c1.
fix test
Explanation of problem
Add week 4 in class hash function
Add hashmap homework
Add chained hash map homework
WIP.  undo changes to linked list
Refactor test
Binary search
Binary search exercise
FIX TEST
Make first hash function spec un-stupid
breadth-first and depth-first search