Strips self-closing tags

Running the task on pages with self-closing tags and piping to another directory strips the "closing" part, i.e., `
` becomes `
`.

Using a modified version of the HTML page you have in the README:

```

p { color: red; }

Test
Is it still there?

```

Note that the `meta` tag and the `br` are self-closing. And run this configuration:

```
gulp.task('inline', function() {
return gulp.src('./tmp/*.html')
.pipe(inlineCss())
.pipe(gulp.dest('./dist'));;
});
```

The output is:

```

Test
Is it still there?

```

I played around with `removeStyleTags` and `removeLinkTags` but the problem didn't change.