Fix minor newline consistency issues in test files (#87)

bench_test.go

@@ -15,6 +15,7 @@ func noErrors(at, depth int) error {
 	}
 	return noErrors(at+1, depth)
 }
+
 func yesErrors(at, depth int) error {
 	if at >= depth {
 		return New("ye error")

errors_test.go

@@ -196,7 +196,6 @@ func TestWithMessage(t *testing.T) {
 			t.Errorf("WithMessage(%v, %q): got: %q, want %q", tt.err, tt.message, got, tt.want)
 		}
 	}
-
 }
 
 // errors.New, etc values are not expected to be compared by value