Stick to tox 1.9.2 until we are ready to upgrade

Author: keimlink

requirements/ci.txt

@@ -1,2 +1,2 @@
 codecov==1.1.8
-tox==1.9.2
+tox==1.9.2  # rq.filter: <2.0.0

setup.py

@@ -28,7 +28,7 @@ def read(*paths):
     'pytest==2.7.0',
     'python-dateutil==2.4.2',
     'six==1.9.0',
-    'tox==1.9.2',
+    'tox==1.9.2',  # rq.filter: <2.0.0
     'virtualenv>=12.0.2,!=12.0.4,!=12.0.5,!=12.0.6,!=12.0.7',
 ]