Update accord to version 0.21.0 🚀

[greenkeeperio-bot]

Hello 👋

🚀🚀🚀

accord just published its new version 0.21.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of accord – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging 🌴

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GitHub Release

• BREAKING: Babel upgrade to v6 changed the package name, which accord's architecture was not prepared to handle, so we have a breaking change. Support for Babel 6 here, but you might have issues with older versions of Babel now. Everything else is fine.
• We now only test with node v4 and up, if you do not plan on upgrading node soon or have it already upgraded, you might need to revert back to 0.20.x if there's a bug that cannot be replicated. In our testing, we only noticed one small one with Babel.
• Bring all other packages up to date, passing tests

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The new version differs by 15 commits .

• 4192516 Merge pull request #132 from jenius/greenkeeper-update-all
• fd78134 0.21.0
• 84daec4 min support node 4
• f98e700 fix csso adapter upgrade
• c8f7050 breaking: babel upgrade to 6
• a07f4c1 address stylus error error
• 0d91cfe upgrade minify-html
• 8b592c3 fix parse5 upgrade issue
• bfc7ad7 chore(package): update dependencies
• a3aba2a Merge pull request #126 from davej/feature/fix-scss-sourcemap-sources
• 5f86a91 scss: convert sourcemap sources to absolute paths
• a05630e Merge pull request #127 from ReadmeCritic/master
• 7ba41ae Update README URLs based on HTTP redirects
• 8eb8f1b Merge pull request #124 from betaorbust/master
• 231985c Fix uglify-js dep. due to NSP security notification.

See the full diff.

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