Better logging for tab encountered error.

I came across this error while transforming some of our comments. This tweaks the error to print the string that is causing the error, so you can more quickly identify it.

I would like to provide an even better error message explaining why and how the user should configure the printer with `tabWidth` but I wasn't sure why this comment node was being processed.

```javascript
/***********
 * 			CALLBACKS.
 **********/
```

Above is the actual comment, can you explain why I need to configure `tabWidth` now when I haven't had to before? Is it as simple as tabs in comments cause problems?

Due to `wrapColumn` I have had to configure the printer.

```javascript
print(fileMetadata.ast, {wrapColumn: 200}).code
```

I guess the configuration triggers processing every node?