External wildcard examples cannot be mixed with any other examples

[mpetrovich]

If you use an external wildcard example, adding an inline or other external example does not work as expected.

For instance, none of these work:

```sample:template.html
```
```sample:files/*
```

```sample.html
<p>Hello, world</p>
```
```sample:files/*
```

where files is a directory containing any number of CSS, JS, or HTML assets.