`geom_bin2d`: wrong geometry size when `bins=[n, 1]`

Example:

```python
data = {
'x': [0, 0, 1, 2],
'y': [0, 0, 1, 2],
}

ggplot(data, aes('x', 'y')) + geom_bin2d(bins=[2, 1]) + geom_point(color="red")
```

Expected:

---

The same problem occurs when we swap `bins` items:

```python
ggplot(data, aes('x', 'y')) + geom_bin2d(bins=[1, 2]) + geom_point(color="red")
```

or when both items are equal to 1:

```python
ggplot(data, aes('x', 'y')) + geom_bin2d(bins=[1, 1]) + geom_point(color="red")
```

In all cases, the tiles should cover all the space where there are points.