`fmap` over a `dict` should `map` over the items, not `starmap`

Instead of
```python
some_dict |> fmap$((k, v) -> (k, v + 1))
```
this change would require
```python
some_dict |> fmap$(def ((k, v)) -> (k, v + 1))
```
which would keep the type signature of `fmap` more consistent.

Note that this would be a breaking change.