Add invoke(), for_each() and for_each_right()

What's the intention here? I don't think Lo-Dash does anything differently if `null` or `undefined` is returned.

Were you trying to do something like this:

```python
method = getattr(item, method_name, None)
if method is None:
    lst.append(item)
else:
    lst.append(method(*args))
```

?