Update typescript to version 2.3.1 🚀

[greenkeeperio-bot]

Hello lovely humans,

typescript just published its new version 2.3.1.

State	Update 🚀
Dependency	typescript
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 typescript.
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!

🌴

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The new version differs by 1053 commits (ahead by 1053, behind by 39).

• 47e5569 Update LKG
• 9ada915 Merge pull request #15381 from Microsoft/revert15104
• fe0a307 Revert "Treat callback parameters as strictly covariant"
• 96a3c91 Revert "Fix callback types to match covariantly"
• 70bb2d3 Revert "Accept new baselines"
• 3abd0c8 Revert "Add tests"
• 42d6a9c Revert "Check callback return values bi-variantly"
• d581bed Revert "Accept new baselines"
• cf17be2 Revert "Add another test case"
• e86512e Revert "Allow callbacks unioned with null and/or undefined"
• 22647bb Revert "Update tests"
• 8a85f4a Update LKG
• 3c3b73e Merge branch 'master' into release-2.3
• a0abadb Merge pull request #15320 from Microsoft/fixTypePredicateThisParameter
• 5783435 Merge pull request #15330 from gcnew/exportConsts

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

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[coveralls]

Coverage remained the same at 100.0% when pulling be35ef2 on greenkeeper-typescript-2.3.1 into 4428bd3 on master.