Drop compatibility for Python <= 3.5

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [0.17.0-dev] - unreleased
 
+### Changed
+
+* **Backwards incompatible.** Lowest compatible Python version is now 3.6.
+
 ## [0.16.0] - 2018-07-23
 
 ### Added

setup.py

@@ -45,8 +45,6 @@ setup(
         'License :: OSI Approved :: BSD License',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3 :: Only',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: Implementation :: CPython',
         'Topic :: Communications',