Update hypothesis to 3.31.0

[pyup-bot]

There's a new version of hypothesis available.
You are currently using 3.30.4. I have updated it to 3.31.0

These links might come in handy: PyPI | Changelog | Repo

Changelog

3.31.0

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This release blocks installation of Hypothesis on Python 3.3, which
:PEP:reached its end of life date on 2017-09-29 <398>.

This should not be of interest to anyone but downstream maintainers -
if you are affected, migrate to a secure version of Python as soon as
possible or at least seek commercial support.

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Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖

[coveralls]

Coverage remained the same at 100.0% when pulling 47e3e2c on pyup-update-hypothesis-3.30.4-to-3.31.0 into 4e445f2 on master.