misc: force Django 1.7 for now

Running with 1.8 yields "ImproperlyConfigured: Creating a ModelForm without
either the 'fields' attribute or the 'exclude' attribute is prohibited; form
ApiUserForm needs updating.".

requirements.txt

@@ -1,4 +1,4 @@
-django >= 1.7
+django >= 1.7, <1.8
 django-jsonresponse >= 0.10, < 0.11
 django-model-utils
 django-jsonfield >= 0.9.3

setup.py

@@ -47,7 +47,7 @@ setup(name='passerelle',
         scripts=['manage.py'],
         include_package_data=True,
         install_requires=[
-            'django >= 1.7',
+            'django >= 1.7, <1.8',
             'django-model-utils',
             'django-jsonresponse==0.10',
             'django-jsonfield >= 0.9.3',