Made TodoItem setters protected.
Added indexLabel, close #154
Merge branch 'staging' into dat/model
Merge pull request #155 from cs2103aug2014-w13-1c/jin/gui

Added indexLabel, close #154
Removed filtering capabilities from model. Passing filtering to TaskController.
Merge branch 'staging' into dat/model
Fix incorrect index
Merge pull request #157 from cs2103aug2014-w13-1c/jin/gui

Fix incorrect index
Fix model.md inconsistencies.
Merge branch 'staging' into dat/model
More comments for ModelUnits
Merge branch 'dat/model'