[updated] Exception Handling for Model Class
Merge branch 'master' of https://github.com/cs2103aug2014-f10-2j/main.git

Conflicts:
	src/main/java/com/epictodo/model/DeadlineTask.java
	src/main/java/com/epictodo/model/TimedTask.java
Revert "[updated] Exception Handling for Model Class"

This reverts commit 122caf64e899901c665e6e1119db2f616edc8429.
[added] New Exceptions to Model Class