Exclude tests from built package

Author: AlexHill

setup.py

@@ -12,7 +12,7 @@
     long_description=long_description,
     long_description_content_type='text/markdown',
     url='https://github.com/alexhill/django-relativity',
-    packages=setuptools.find_packages(),
+    packages=setuptools.find_packages(exclude=['tests']),
     install_requires=['django>=1.11'],
     classifiers=[
         'Development Status :: 4 - Beta',