Marking this library as Production/Stable for PyPI

FYI: https://pypi.org/classifiers/

Author: rayluo

setup.py

@@ -53,7 +53,7 @@
     author_email='[email protected]',
     url='https://github.com/AzureAD/microsoft-authentication-library-for-python',
     classifiers=[
-        'Development Status :: 4 - Beta',
+        'Development Status :: 5 - Production/Stable',
         'Programming Language :: Python',
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',