Merge pull request #229 from PetrDlouhy/fix_css_class

Get css_class from self - fixes integration with django-crispy-forms

smart_selects/widgets.py

@@ -133,6 +133,7 @@ def render(self, name, value, attrs=None, choices=()):  # noqa: C901
                     final_choices.append(ch)
         self.choices = final_choices
 
+        attrs.update(self.attrs)
         attrs["data-chainfield"] = chained_field
         attrs["data-url"] = url
         attrs["data-value"] = "null" if value is None or value == "" else value