Version v0.2 of Tommy Chatbot

Full implementation of Tommy Chatbot
Functions include:
List, Bye, Delete, Mark, Unmark, Find
Add Todo, Add Deadline, Add Event

Types of Tasks:
Todo, Deadline, Event

Improved GUI for better user experience.

Version v0.1 of Duke Chatbot

Basic implementation of Duke Chatbot
Functions include:
List, Bye, Delete, Mark, Unmark
Add Todo, Add Deadline, Add Event

Types of Tasks:
Todo, Deadline, Event