add Python 3.7 to the setup.py classifiers

Author: basnijholt

setup.py

@@ -56,6 +56,7 @@ def get_version_and_cmdclass(package_name):
         'License :: OSI Approved :: BSD License',
         'Intended Audience :: Science/Research',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
     ],
     packages=find_packages('.'),
     install_requires=install_requires,