Update @types/chai to the latest version 🚀

[greenkeeper[bot]]

Version 4.0.4 of @types/chai just got published.

Dependency	@types/chai
Current Version	4.0.3
Type	devDependency

The version 4.0.4 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 @types/chai. 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.

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Not sure how things should work exactly?

There is a collection of [frequently asked questions](https://greenkeeper.io/faq.html) and of course you may always [ask my humans](https://github.com/greenkeeperio/greenkeeper/issues/new).

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Your Greenkeeper Bot :palm_tree:

[codecov-io]

Codecov Report

Merging #50 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #50   +/-   ##
======================================
  Coverage    96.8%   96.8%           
======================================
  Files          50      50           
  Lines        1440    1440           
  Branches      205     205           
======================================
  Hits         1394    1394           
  Misses         13      13           
  Partials       33      33

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