optimize the _.max and _.min

I'm just thinking that we don't need below  `Conditional (Ternary) Operator (?:)` in `each` function and run it eveytime, we don't need to define the ```var computed``` also.
```javascript
var computed = iterator ? iterator.call(context, value, index, list) : value;
```

In addition, for the code below, we create a new object and set it to `result` every time once the `computed` matches the condition `>= result.computed` or `< result.computed`, it's beatutiful code, but we don't need to creat the object, reset the values of `result ` can be work. but as it looks good, so I didn't update this part, any ideas?
```javascript
computed < result.computed && (result = {value : value, computed : computed});
```