Change the Development Status from beta to stable

Author: Hasenpfote

setup.py

@@ -50,7 +50,7 @@ def exclude_packages(names):
             'Programming Language :: Python :: 3.7',
             'License :: OSI Approved :: MIT License',
             'Operating System :: OS Independent',
-            'Development Status :: 4 - Beta',
+            'Development Status :: 5 - Production/Stable',
             'Environment :: Other Environment',
             'Intended Audience :: Developers',
             'Topic :: Software Development :: Libraries :: Python Modules',