Test + bug fixes

Sources/Engine/Square.swift

@@ -5,11 +5,12 @@ public struct Square: Equatable {
 		public let rank: UInt8
 
 		public var index: Int {
-			return Int(file * rank) - 1
+			let r = (8 - rank) % 8
+			return Int(8*r+file-1)
 		}
 
 		public static func == (lhs: Position, rhs: Position) -> Bool {
-			return lhs.rank == rhs.rank && lhs.file == rhs.file
+			return lhs.index == rhs.index
 		}
 	}