Fix root URL warning.

Nemo warns about (and corrects) an explicit base_url="/"
parameter, requiring an empty string instead. However, all
TestSimpleQuery tests pass this as part of their instance
config, cluttering the output with warnings. This is
especially obvious with the pytest wrapper.

Avoid the warning by passing the indicated base_url="" instead.

tests/test_query/test_interface.py

@@ -55,7 +55,7 @@ def setUp(self):
         logger = logging.getLogger('my-logger')
         logger.propagate = False
         self.nautilus = CtsCapitainsLocalResolver(["tests/test_data/interface/latinLit"], logger=logger)
-        self.nemo = Nemo(app=self.app, resolver=self.nautilus, base_url="/")
+        self.nemo = Nemo(app=self.app, resolver=self.nautilus, base_url="")
         self.query = SimpleQuery(
             [
                 self.one,