Drupal 8.6 (islandora-deprecated#23)

* Honor .env files and suggest usage (drupal-composer#351)

* Remove extra whitespace (drupal-composer#371)

* Updated argument name

* Bump minimal version

* Bump minimal version to 8.5.3

* Fix installer path for drush commandfiles.

* Update drupal-composer/drupal-scaffold

drupal-composer/drupal-scaffold is a full featured plugin and provides its own command.

* Fix tests on Travis CI (drupal-composer#405)

* Copy the editor config and gitattributes from drupal to the root. (drupal-composer#404)

* Remove "drupal-scaffold" from scripts (drupal-composer#275)

* Fix typo in README.md

* Remove unused use statement. (drupal-composer#406)

* Adjust default core patch level to -p2. (drupal-composer#418)

* Bump minimum required composer-patches version to support default patch level (drupal-composer#410)

* Update composer.json to require latest stable version of Drupal (drupal-composer#424)

* Updating lock file

* Adding drupal-scaffold back in so it works with a lockfile

* drupal-scaffold is now @composer drupal:scaffold