Fix loss of whitespace btwn inline tags

Discovered in https://github.com/bootstrap-ruby/rails-bootstrap-forms. This fix is required by 832cf8752ab2d8ae52aa208131a2309f029e9e22.

Previously, the following

```
<div><label>Label</label><input type="text"/> <span>span</span></div>
```

would result in `Labelspan` instead of `Label span`