Update sinon to version 2.3.1 🚀

[greenkeeperio-bot]

🚨🔥⚠️ Action required: Switch to the new Greenkeeper now! 🚨🔥⚠️
This version of Greenkeper will be shutdown on May 31st.
With Integrations first-class bot support landed on GitHub and we’ve rewritten Greenkeeper to take full advantage of it. Simpler setup, fewer pull-requests, faster than ever.

---

Hello lovely humans,

sinon just published its new version 2.3.1.

State	Update 🚀
Dependency	sinon
New version	2.3.1
Type	devDependency

This version is not covered by your current version range.

Without accepting this pull request your project will work just like it did before. There might be a bunch of new features, fixes and perf improvements that the maintainers worked on for you though.

I recommend you look into these changes and try to get onto the latest version of sinon.
Given that you have a decent test suite, a passing build is a strong indicator that you can take advantage of these changes by merging the proposed change into your project. Otherwise this branch is a great starting point for you to work on the update.

Do you have any ideas how I could improve these pull requests? Did I report anything you think isn’t right?
Are you unsure about how things are supposed to work?

There is a collection of frequently asked questions and while I’m just a bot, there is a group of people who are happy to teach me new things. Let them know.

Good luck with your project ✨

You rock!

🌴

---

GitHub Release

• Make calledAfter symetric with calledBefore (#1407)

---

The new version differs by 723 commits (ahead by 723, behind by 46).

• 94f422c Update docs/changelog.md and set new release id in docs/_config.yml
• 69bf8f2 Add release documentation for v2.3.1
• eee4564 2.3.1
• 0dc2505 Update Changelog.txt and AUTHORS for new release
• 36c6cdc Merge pull request #1407 from lucasfcosta/simmetric-callAfter
• 5301cc1 Merge pull request #1420 from mroderick/remove-issue-397-test
• 05e2d11 Remove test for issue 397
• 64d51be Update docs/changelog.md and set new release id in docs/_config.yml
• d4b30b0 Add release documentation for v2.3.0
• 8d64248 2.3.0
• e137139 Update Changelog.txt and AUTHORS for new release
• 55dc491 Merge pull request #1416 from lucasfcosta/refactor-sandbox-stub
• fb514cf Merge pull request #1415 from mroderick/style-improvements
• 06bf652 Merge pull request #1414 from mroderick/add-related-libraries-to-how-to-page
• 746de3f Force fenced code blocks to use smaller font

There are 250 commits in total. See the full diff.

[coveralls]

Coverage remained the same at 100.0% when pulling 6cc8d51 on greenkeeper-sinon-2.3.1 into fd55199 on master.