Use existing requirements

Signed-off-by: Michal Čihař <michal@cihar.com>

.scrutinizer.yml

@@ -16,7 +16,8 @@ build:
     dependencies:
         before:
             - pip install https://github.com/translate/translate/zipball/de3f080abf6f2fecfca97d283a58eb6824d8078e
-            - pip install Django Whoosh lxml Pillow six python-dateutil python-social-auth django-crispy-forms oauthlib django_compressor coverage chardet
+            - pip install coverage
+            - pip install -r requirements-optional.txt
         override:
             - true
     tests: