Added a new error location: UNDO
Reverted Task back to original version, with the new accessors
Working on Undo
Merge branch 'master' of https://github.com/cs2103aug2014-t7-2/main

# By Yui Wei
# Via Yui Wei
* 'master' of https://github.com/cs2103aug2014-t7-2/main:
  sort works! i think.