Remove dependency on FileUtils.

We now use our own implementation: RSpec::Support::DirectoryMaker
instead which implements mkdir_p for us.
Changelog entry for #1565

Conflicts:
	Changelog.md
Merge pull request #1565 from rspec/remove-fileutils

Remove fileutils
Fix color on Shared Example Group failure.

Now is white to separate it from the stack trace.
Add a changelog entry for #1593
Pass the colorizer around correctly in Failure Notification.