Revert switch to python setup.py test in tox.ini.

This had more of a purpose when we were moving mock to test_requires. I'll reintroduce this in the separate PR for that.

Also bring back the testing extra in tox for now.

tox.ini

@@ -8,20 +8,23 @@
 skipsdist = true
 envlist = py{26,27,33,34,35},py{26,27}-oldest,cover,lint
 
+# nosetest -v => more verbose output, allows to detect busy waiting
+# loops, especially on Travis
+
 [testenv]
 # packages installed separately to ensure that downstream deps problems
 # are detected, c.f. #1002
 commands =
-    pip install -e acme
+    pip install -e acme[testing]
-    python acme/setup.py test
+    nosetests -v acme
-    pip install -e .
+    pip install -e .[testing]
-    python setup.py test
+    nosetests -v letsencrypt
     pip install -e letsencrypt-apache
-    python letsencrypt-apache/setup.py test
+    nosetests -v letsencrypt_apache
     pip install -e letsencrypt-nginx
-    python letsencrypt-nginx/setup.py test
+    nosetests -v letsencrypt_nginx
     pip install -e letshelp-letsencrypt
-    python letshelp-letsencrypt/setup.py test
+    nosetests -v letshelp_letsencrypt
 
 setenv =
     PYTHONPATH = {toxinidir}
@@ -37,18 +40,18 @@ deps =
 
 [testenv:py33]
 commands =
-    pip install -e acme
+    pip install -e acme[testing]
-    python acme/setup.py test
+    nosetests -v acme
 
 [testenv:py34]
 commands =
-    pip install -e acme
+    pip install -e acme[testing]
-    python acme/setup.py test
+    nosetests -v acme
 
 [testenv:py35]
 commands =
-    pip install -e acme
+    pip install -e acme[testing]
-    python acme/setup.py test
+    nosetests -v acme
 
 [testenv:cover]
 basepython = python2.7