Remove Python 3.4 from setup.cfg

Now that we dropped support for Windows XP, we can no longer guarantee support for all Windows versions that Python 3.4 supports.

Also see #548.

setup.cfg

@@ -16,7 +16,6 @@ classifiers =
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.4
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7