lower python version to 3.6

in order to allow definitions to be used with python 3.6

Author: anton-b

setup.py

@@ -13,7 +13,7 @@
     license='MIT license',
     author='Alert Logic Inc.',
     author_email='[email protected]',
-    python_requires='>=3.7',
+    python_requires='>=3.6',
     classifiers=[
         'Development Status :: 3 - Alpha',
         'Intended Audience :: Developers',