Add uritemplate as a dependency.

We removed uritemplate from oauth2client, so now we re-add it as a normal
python package dependency.
diff --git a/tox.ini b/tox.ini
index aa1b36c..b7c6591 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@
        django==1.2
        webtest
        nose
+       uritemplate
 setenv = PYTHONPATH=../google_appengine
 
 [testenv:py26]