use just the page part of the path in breadcrumbs

rather than showing the full path (e.g. /foo/bar/baz) in breadcrumbs
when the page doesn't have a Title, show just the leaf (baz)

Closes #4

incorporealcms/pages.py

@@ -130,5 +130,13 @@ def generate_parent_navs(path):
         with app.open_instance_resource(path, 'r') as entry_file:
             entry = entry_file.read()
         _ = Markup(md.convert(entry))
-        page_name = " ".join(md.Meta.get('title')) if md.Meta.get('title') else request_path
+        page_name = (" ".join(md.Meta.get('title')) if md.Meta.get('title')
+                     else request_path_to_breadcrumb_display(request_path))
         return generate_parent_navs(parent_resource_path) + [(page_name, request_path)]
+
+
+def request_path_to_breadcrumb_display(path):
+    """Given a request path, e.g. "/foo/bar/baz/", turn it into breadcrumby text "baz"."""
+    undired = path.rstrip('/')
+    leaf = undired[undired.rfind('/'):]
+    return leaf.strip('/')