Documentation bug in pandas.api.types.is_scalar

#### Example

The first example is:

```
>>> dt = pd.datetime.datetime(2018, 10, 3)
>>> pd.is_scalar(dt)
True
```
#### Problem description

`is_scalar` is not a member of `pd`:

```
AttributeError: module 'pandas' has no attribute 'is_scalar'
```

#### Expected

`pd.api.types.is_scalar(...)`
