Tweak priority API's for offseting

Source/ConstraintMakerPriortizable.swift

@@ -31,8 +31,8 @@
 public class ConstraintMakerPriortizable: ConstraintMakerFinalizable {
     
     @discardableResult
-    public func priority(_ amount: ConstraintPriority) -> ConstraintMakerFinalizable {
-        self.description.priority = amount.value
+    public func priority(_ amount: ConstraintPriority, offset: Float = 0) -> ConstraintMakerFinalizable {
+        self.description.priority = amount.value + offset
         return self
     }
     

Source/ConstraintPriority.swift

@@ -28,7 +28,7 @@
 #endif
 
 
-public struct ConstraintPriority : ExpressibleByFloatLiteral, Strideable, Equatable {
+public struct ConstraintPriority : ExpressibleByFloatLiteral, Equatable {
     public typealias FloatLiteralType = Float
     
     public let value: Float
@@ -62,14 +62,6 @@ public struct ConstraintPriority : ExpressibleByFloatLiteral, Strideable, Equata
         return 250.0
     }
     
-    public func advanced(by n: Float) -> ConstraintPriority {
-        return ConstraintPriority(self.value + n)
-    }
-    
-    public func distance(to other: ConstraintPriority) -> Float {
-        return other.value - self.value
-    }
-    
     public static func ==(lhs: ConstraintPriority, rhs: ConstraintPriority) -> Bool {
         return lhs.value == rhs.value
     }