Add benchmark results to bottom

difference_of_squares.go

@@ -29,3 +29,10 @@ func SumOfSquares(n int) int {
 func Difference(n int) int {
 	return SquareOfSums(n) - SumOfSquares(n)
 }
+
+// Iteration 1 benchmark:
+//
+// PASS
+// BenchmarkSquareOfSums-12	30000000	        56.5 ns/op
+// BenchmarkSumOfSquares-12	20000000	        63.8 ns/op
+// BenchmarkDifference-12  	20000000	       113 ns/op