Fourth release of the JAR file

Update on this release:
-Fix bug when lacking the description of event, deadline and todo

Third release of the JAR file

Updates on this release:
-Handle exceptions on done, delete, todo, event, deadline and find
-Add 'find' to allow finding by a keyword in the list events
-Update the "help" command
-Refactor the code into packages for developers

Fix bug on updating output file when deleting a task

v0.2

Debug on updating output file after delete a task

First release of the JAR file for iP Project

Merge branch 'branch-Level-7'

# Conflicts:
#	src/main/java/Duke.java
Implement ArrayList for reading files