Add stable status classifier to setup.py

Author: adamnsch

setup.py

@@ -10,6 +10,7 @@
     version = f.readline().strip().split()[-1][1:-1]
 
 classifiers = [
+    "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: Apache Software License",