Update postcss to the latest version 🚀

Version 7.0.0 of postcss was just published.

Dependency	postcss
Current Version	6.0.23
Type	devDependency

The version 7.0.0 is not covered by your current version range.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

It might be worth looking into these changes and trying to get this project onto the latest version of postcss.

If you have a solid test suite and good coverage, a passing build is a strong indicator that you can take advantage of these changes directly by merging the proposed change into your project. If the build fails or you don’t have such unconditional trust in your tests, this branch is a great starting point for you to work on the update.

Release Notes

7.0 “President Amy”

PostCSS 7.0 dropped Node.js 4 support and brought small features.

Breaking Changes

We removed Node.js 4 and Node.js 9 support since it doesn’t have security updates anymore.

We removed IE and “dead” browsers (without security updates) from Babel’s Browserslist:

last 2 version
not dead
not Explorer 11
not ExplorerMobile 11

New Features

@nikhilgaba added cute thing for plugin developers. If an error was happened in Container#walk() circle, PostCSS will show in stack trace CSS node, which causes this error:

TypeError: Cannot read property '0' of undefined
    at /home/ai/Dev/test/app.css:10:4
    at plugin (plugin.js:2:4)
    at runPostCSS (runner.js:2:1)

@igorkamyshev added finally method to LazyResult to make it compatible with the latest Promise API.

Other Changes

Client-side size was reduced by Size Limit feedback.
Add warning on calling PostCSS without plugins and syntax options.

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postcss / postcss-load-config