Make ConstraintViewDSL content priorities nonmutating (#586)

Source/ConstraintViewDSL.swift

@@ -55,7 +55,7 @@ public struct ConstraintViewDSL: ConstraintAttributesDSL {
         get {
             return self.view.contentHuggingPriority(for: .horizontal).rawValue
         }
-        set {
+        nonmutating set {
             self.view.setContentHuggingPriority(LayoutPriority(rawValue: newValue), for: .horizontal)
         }
     }
@@ -64,7 +64,7 @@ public struct ConstraintViewDSL: ConstraintAttributesDSL {
         get {
             return self.view.contentHuggingPriority(for: .vertical).rawValue
         }
-        set {
+        nonmutating set {
             self.view.setContentHuggingPriority(LayoutPriority(rawValue: newValue), for: .vertical)
         }
     }
@@ -73,7 +73,7 @@ public struct ConstraintViewDSL: ConstraintAttributesDSL {
         get {
             return self.view.contentCompressionResistancePriority(for: .horizontal).rawValue
         }
-        set {
+        nonmutating set {
             self.view.setContentCompressionResistancePriority(LayoutPriority(rawValue: newValue), for: .horizontal)
         }
     }
@@ -82,7 +82,7 @@ public struct ConstraintViewDSL: ConstraintAttributesDSL {
         get {
             return self.view.contentCompressionResistancePriority(for: .vertical).rawValue
         }
-        set {
+        nonmutating set {
             self.view.setContentCompressionResistancePriority(LayoutPriority(rawValue: newValue), for: .vertical)
         }
     }