Allow using icons without custom class

app/views/icons/foo.sh

@@ -0,0 +1,7 @@
+for file in *.erb; do
+  if [ -f "$file" ]; then
+    sed -i'.bak' 's/<%= *custom_class *%>/<%= local_assigns[:custom_class] %>/g' "$file"
+    echo "Updated $file"
+    rm "${file}.bak"
+  fi
+done