Use py.test for testing

.travis.yml

@@ -13,6 +13,6 @@ before_script:
 script:
     - make
     - make compress
-    - coverage run manage.py test -v 2
+    - coverage run py.test
 after_success:
     - coveralls

src/pytest.ini

@@ -0,0 +1,3 @@
+[pytest]
+DJANGO_SETTINGS_MODULE=pretix.settings
+

src/requirements/testing.txt

@@ -6,6 +6,8 @@ flake8
 coveralls
 coverage
 selenium
+pytest
+pytest-django
 # PyVirtualDisplay
 # -e git+https://github.com/pretix/sauceclient.git@master#egg=sauceclient
 # travis