Update babel-polyfill to the latest version 🚀

[greenkeeper[bot]]

Version 6.26.0 of babel-polyfill just got published.

Dependency	babel-polyfill
Current Version	6.23.0
Type	devDependency

The version 6.26.0 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 babel-polyfill. 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[bot]]

Codecov Report

Merging #49 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #49   +/-   ##
======================================
  Coverage    85.4%   85.4%           
======================================
  Files          54      54           
  Lines        1309    1309           
======================================
  Hits         1118    1118           
  Misses        191     191