Added due/by keywords. Close #151
Fix indentation
add controllers.md
Added an 'all' keyword
Added done/undone keywords
Added a public API in CommandController to change the savefile location
Initialize ActionController in CommandController's constructor
Declare commandParser to become a local variable
Added the done/undone functionality back
Changing savefile location now works again woohoo
Merge pull request #166 from cs2103aug2014-w13-1c/jin/gui

Reimplemented Ryan's reverted commit