[Twisted-Python] Drop support for Python 3.3

I submitted this patch to drop support for Python 3.3: https://github.com/twisted/twisted/pull/943 1. Python 3.3 was declared EOL on Sep. 29, 2017 2. In terms of major Linux distributions, Python 3.4 came with Python 3.4 is in Debian 8, Ubuntu 14.04, Fedora 21 So after this patch, Twisted would run on: Python 2.7 and Python 3.4+ Thoughts? -- Craig