-Uniquified the table. It's no longer possible to push multiple elements with the same key. (Was never prudent to do so to begin with, since you could only access the most recently pushed element.)
 Attempting to push the same key twice will throw a duplicate_entry() exception.
-Attempting to pop a nonexistent element will throw a no_such_element() exception.
-Changed pop() to take an object of type T as its argument, rather than either an int or a string.
-Fixed issue where calling pop() would remove the element from one key-table but not from the other
-Fixed issue where calling pop() could reduce the size tracking more than it should
-Added a resort() function to be called any time the keys change on an object to ensure the table remains functional
-Corrected a small memory leak