groupby now supports attributes of attributes. This fixes #10
diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index 657a8bc..a4b5a2f 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -13,7 +13,7 @@
from copy import deepcopy
from jinja2 import nodes
from jinja2.nodes import EvalContext
-from jinja2.visitor import NodeVisitor, NodeTransformer
+from jinja2.visitor import NodeVisitor
from jinja2.exceptions import TemplateAssertionError
from jinja2.utils import Markup, concat, escape, is_python_keyword, next