UI package now contains TabCompletion task which utilises Tab Completion in Jline 1.0. When user presses tab, a list of available commands would appear. Tasker also now supports the 'help' command which shows users what each command does and 'exit' command which helps to exit the program.
Merge branch 'master' of https://github.com/cs2103aug2014-T13-2J/main

# By mervynwee
# Via mervynwee
* 'master' of https://github.com/cs2103aug2014-T13-2J/main:
  Replace getTime with getTimeAndTrimUserInput. Add two new test cases to test the added feature where users can input  "add meeting on Thursday" and "add meeting next Thursday" in AddParserTest.java.
  Implement the case where users input "add meeting on Thursday" or "add meeting next Thursday". Implement a function isDayOfWeek to support this feature. Rename getTime to getTimeAndTrimUserInput. Add new String constant MESSAGE_NEGATIVE_DIFFERENCE_IN_DAYS.
  Refactor AddParser.java, extract the initialization of the date and time components from each if else branch and put it at the end of the parse function. Modify the "from.. ..to" case to allow users to input the following format "add meeting on 22/10 from 11am to 2pm". This used to be an invalid format, requiring users to input "add meeting from 22/10 11am to 22/10 2pm.