Added precision on dependencies

Author: Joachim Jablon

setup.py

@@ -42,7 +42,8 @@
         'django_readonly_field',
     ],
     include_package_data=True,
-    install_requires=[],
+    install_requires=["Django>=1.8,<1.11"],
+    test_requires=["tox"],
     license="MIT",
     zip_safe=False,
     keywords='django-readonly-field',