Add requires.io filter

Author: wsanchez

tox.ini

@@ -224,7 +224,7 @@ basepython = {[default]basepython}
 skip_install = True
 
 deps =
-    coverage==4.5.4  # coverage 5.0 drops support for Python 3.4
+    coverage==4.5.4  # rq.filter: <5  # coverage 5.0 drops Python 3.4 support
 
 setenv =
     {[default]setenv}