downgrade python requirement to 3.4

 * for testing with python3 albula, which has been built
   against python3.4

Author: JunAishima

setup.py

@@ -7,7 +7,7 @@
 # NOTE: This file must remain Python 2 compatible for the foreseeable future,
 # to ensure that we error out properly for people with outdated setuptools
 # and/or pip.
-min_version = (3, 6)
+min_version = (3, 4)
 if sys.version_info < min_version:
     error = """
 qt-epics does not support Python {0}.{1}.