Fix nullability annotation on willUpdateDataModel

Return value is optional

Update podspec

Set deployment target back to 6.1

Share TLIndexPathTools scheme for Carthage

Make hasChanges internally readwrite

Reduce deployment target of Settings example project to 7.0

Increment version number

Ignore warning on call to private setModifiedItems method

Add `shouldChangeNode` option to `TLTreeTableViewControllerDelegate`

Improve performance of TLIndexPathUpdates initializer