Use constraints for all the things

This configures tox to use upper-constraints for everything.

Change-Id: I5611d0d9052d26a2e9e0b63fc302e4c65b83ba7c

tox.ini

@@ -2,6 +2,7 @@
 envlist = pep8,py27,py34
 
 [testenv]
+install_command = pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 usedevelop = True
 deps =
     -r{toxinidir}/requirements.txt
@@ -22,4 +23,4 @@ commands =
 
 [flake8]
 max-complexity=15
-show-source = True
+show-source = True