Rename "css" to "classes"

aleksis/core/templates/components/materialize-chips.html

-<div class="chip {{ css }}">
+<div class="chip {{ classes }}">
   {% if img %}
-    <img src="{{ img }}" alt="{{ alt }}">
+    <img class="{{ img_classes }}" src="{{ img }}" alt="{{ alt }}">
   {% endif %}
   {{ content }}
   {% if close %}