Hardcode django-representatives{,-votes} version

Otherwise tests might become broken as a side effect of an upgrade in
these packages. And that's hard to figure out ;)

setup.py

@@ -15,8 +15,8 @@ setup(name='political-memory',
         'django-compressor>=1.6,<1.7',
         'django-datetime-widget>=0.9,<1.0',
         'django-filter>=0.11,<0.12',
-        'django-representatives-votes>=0.0.13',
-        'django-representatives>=0.0.14',
+        'django-representatives-votes==0.0.13',
+        'django-representatives==0.0.14',
         'django-taggit>=0.17,<0.18',
         'django>=1.8,<1.9',
         'djangorestframework>=3.2.0,<3.3.0',