Add benchmark for ToBool

```
BenchmarkTooBool-4   	  500000	      2781 ns/op	      49 B/op	       3 allocs/op
```

cast_test.go

@@ -143,8 +143,8 @@ func TestSlices(t *testing.T) {
 	assert.Equal(t, []int{2, 3}, ToIntSlice([2]string{"2", "3"}))
 	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]bool{true, false, true}))
 	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]interface{}{true, false, true}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]int{1,0,1}))
-	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]string{"true","false","true"}))
+	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]int{1, 0, 1}))
+	assert.Equal(t, []bool{true, false, true}, ToBoolSlice([]string{"true", "false", "true"}))
 }
 
 func TestToBool(t *testing.T) {
@@ -168,6 +168,14 @@ func TestToBool(t *testing.T) {
 	assert.Equal(t, ToBool(-1), true)
 }
 
+func BenchmarkTooBool(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if !ToBool(true) {
+			b.Fatal("ToBool returned false")
+		}
+	}
+}
+
 func TestIndirectPointers(t *testing.T) {
 	x := 13
 	y := &x