Add "-v" to the pytest command when run in tox

tox.ini

@@ -13,7 +13,7 @@ max-line-length = 100
 usedevelop = true
 deps = -r{toxinidir}/test-requirements.txt
 commands =
-    py.test {posargs}
+    py.test -v {posargs}
 
 [testenv:coverage]
 basepython = python2