Change supported python

Author: JakubAndrysek

setup.py

@@ -17,11 +17,10 @@ def readme():
     author='Jakub Andrýsek',
     author_email='[email protected]',
     license='MIT',
-    python_requires='>=3.6',
+    python_requires='>=3.7',
     install_requires=['mkdocs'],
     classifiers=[
         'License :: OSI Approved :: MIT License',
-        'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',