Update fs-extra requirement to ^6.0.0

[dependabot-preview]

Updates the requirements on fs-extra to permit the latest version.

Changelog

Sourced from fs-extra's changelog.

6.0.0 / 2018-05-01

• Drop support for Node.js versions 4, 5, & 7 (#564)
• Rewrite move to use fs.rename where possible (#549)
• Don't convert relative paths to absolute paths for filter (#554)
• copy*'s behavior when preserveTimestamps is false has been OS-dependent since 5.0.0, but that's now explicitly noted in the docs (#563)
• Fix subdirectory detection for copy* & move* (#541)
• Handle case-insensitive paths correctly in copy* (#568)

5.0.0 / 2017-12-11

Significant refactor of copy() & copySync(), including breaking changes. No changes to other functions in this release.

Huge thanks to [manidlou](https://github.com/manidlou) for doing most of the work on this release.

• The filter option can no longer be a RegExp (must be a function). This was deprecated since fs-extra v1.0.0. #512
• copy()'s filter option can now be a function that returns a Promise. #518
• copy() & copySync() now use fs.copyFile()/fs.copyFileSync() in environments that support it (currently Node 8.5.0+). Older Node versions still get the old implementation. #505
• Don't allow copying a directory into itself. #83
• Handle copying between identical files. #198
• Error out when copying an empty folder to a path that already exists. #464
• Don't create dest's parent if the filter function aborts the copy() operation. #517
• Fix writeStream not being closed if there was an error in copy(). #516

4.0.3 / 2017-12-05

• Fix wrong chmod values in fs.remove() #501
• Fix TypeError on systems that don't have some fs operations like lchown #520

4.0.2 / 2017-09-12

• Added EOL option to writeJson* & outputJson* (via upgrade to jsonfile v4)
• Added promise support to fs.copyFile() in Node 8.5+
• Added .js extension to main field in package.json for better tooling compatibility. #485

4.0.1 / 2017-07-31

Fixed

• Previously, ensureFile() & ensureFileSync() would do nothing if the path was a directory. Now, they error out for consistency with ensureDir(). #465, #466, #470

4.0.0 / 2017-07-14

Changed

... (truncated)

Commits

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