Chores: Log value of a superClass when it's invalid and rename UniqueIdGenerator to UniqueIdentifierGenerator in docs

See title
How about now?

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Using template literals still kept it a > 80 chars, and a new line creates a lot of whitespace in a template literal because of indentation

```js
throw new $TypeError(`Super expression must either be null or a function, 
        not ${typeof superClass}.`);
```