fix tests failing (for now)

hypothesis introduced a regression in 3.29.0 (or at least changed
behaviour). Until I have found the problem I will pin it to the last
working version.

Also two tests should be prevented from failing when they are slow.

setup.py

@@ -132,7 +132,7 @@ setup(
         'nose',
         'scripttest',
         'mock',
-        'hypothesis',
+        'hypothesis<=3.28.3',
         'flake8'
     ],
     cmdclass={'test': Tox},