Fix uncontrolled dependencies, update responsediff

.travis.yml

 sudo: false
 language: python
 env:
-- DJANGO="django>1.8,<1.9" DJANGO_SETTINGS_MODULE=representatives_votes.tests.settings
+- DJANGO_SETTINGS_MODULE=representatives_votes.tests.settings
 python:
 - "2.7"
-before_install:
-- pip install codecov
 install:
-- pip install $DJANGO pep8 flake8 pytest-django pytest-cov codecov django-responsediff==0.4.0 mock
-- pip install https://github.com/political-memory/django-representatives/archive/parltrack.tar.gz#egg=django-representatives
-- pip install -e .[api]
+- pip install -e .[api,testing]
 script:
 - django-admin migrate
 - flake8 representatives_votes/ --exclude migrations --ignore E128

setup.py

@@ -12,15 +12,26 @@ setup(
     license='GPLv3',
     keywords='django government parliament votes',
     install_requires=[
-        'django-representatives>=0.0.15',
-        'py-dateutil',
-        'pytz',
-        'ijson',
+        'django>1.8,<1.9',
+        'django-representatives>=0.0.23',
+        'py-dateutil>=2,<3',
+        'ijson>=2,<3',
+        'pytz',  # Always use up-to-date TZ data
     ],
     extras_require={
         'api': [
-            'django-filter',
-            'djangorestframework',
+            'django-filter>=0.13,<0.14',
+            'djangorestframework>=3,<4',
+        ],
+        'testing': [
+            'codecov>=2,<3',
+            'flake8>=2,<3',
+            'mock>=2,<3',
+            'pep8>=1,<2',
+            'pytest>=2,<3',
+            'pytest-django>=2,<3',
+            'pytest-cov>=2,<3',
+            'django-responsediff>=0.6,<0.7'
         ]
     },
     entry_points={