Add InstalledAppFlow (#128)

diff --git a/tox.ini b/tox.ini
index 27f7d87..0a0d806 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,16 +3,16 @@
 
 [testenv]
 deps =
+  certifi
   flask
   mock
+  oauth2client
   pytest
   pytest-cov
   pytest-localserver
-  urllib3
-  certifi
   requests
   requests-oauthlib
-  oauth2client
+  urllib3
   grpcio; platform_python_implementation != 'PyPy'
 commands =
   py.test --cov=google.auth --cov=google.oauth2 --cov=tests {posargs:tests}