Fixed a _size bug in insert, and check invalid input in insert now. Also implemented removeLast.
Changed remove(T& element) to removeFirstElement(const T& element), and changed name of removeLastOccurrence to removeLastElement. Implemented removeFirstElement.
Changed removeLastElement to take a const. Implemented the contents of the method.
Changed signature of set to return by value, and to take a const T. Implemented body of function.
Added another error check in everything that has an index besides insert.
Filled in operator=
Added operator ==
Renamed variable in operator== and added operator!=