Make TextDocument.swift compile in Xcode 6.1 GM2
Make DocCollectionViewController.swift compile in Xcode 6.1 GM2
Make TextEditorViewController.swift compile in Xcode 6.1 GM2
Make MainViewController.swift compile in Xcode 6.1 GM2
Make ObservationHelper.swift compile in Xcode 6.1 GM2
Make ICloudManager.swift compile in Xcode 6.1 GM2
Make DocumentsManager.swift compile in Xcode 6.1 GM2
Make DocCollectionViewController.swift compile in Xcode 6.1 GM2
Use 'let' in place of 'var' wherever possible
Bump up required Xcode version