FormationLayout

FormationLayout is the top level layout class for one root view.

Features:

• FormationLayout takes a UIView as its rootView.
• translatesAutoresizingMaskIntoConstraints of rootView is not set to false by default but can be set in constructor.
• translatesAutoresizingMaskIntoConstraints of subviews will be set to false automatically.
• Subviews with no superView will be added to rootView automatically.