Fixed bug on update & changed priority algorithm
Changed date and priority parsing algorithm

only the last "start", "end" and "priority" keywords will be checked
Added parsing for sorting method
Preparing for searching with date
Merge branch 'staging' into ryan/controller

Conflicts:
	src/app/controllers/CommandParser.java
	src/app/helpers/CommandObject.java
Merge pull request #237 from cs2103aug2014-w13-1c/ryan/controller

Changed parsing algorithm, added parsing for sort, preparing keywords for search by dates