Changelog:
==========
-improves shrinking in cases involving 'slips' from one strategy to another.
-reduces the range of :class:'python:datetime.datetime' generated by :
func:'~hypothesis.extra.django.from_model' in order to avoid
https://code.djangoproject.com/ticket/35683.
Signed-off-by: Wang Mingyu <wangmy@fujitsu.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>