Declare compatibility with versions of Drush and CSS selector that are compatible with Drupal 8.4 and earlier.

Author: pfrenssen

composer.json

@@ -21,7 +21,7 @@
         "drupal-composer/drupal-scaffold": "^2.2",
         "drupal/console": "^1.0.1",
         "drupal/core": "~8.0",
-        "drush/drush": "~8.0|^9.0.0-beta4",
+        "drush/drush": "~8.0|^9.0.0-beta7",
         "webflo/drupal-finder": "^1.0.0",
         "webmozart/path-util": "^2.3"
     },
@@ -32,7 +32,7 @@
         "jcalderonzumba/mink-phantomjs-driver": "~0.3.1",
         "mikey179/vfsstream": "~1.2",
         "phpunit/phpunit": ">=4.8.28 <5",
-        "symfony/css-selector": "~2.8"
+        "symfony/css-selector": "~2.8|~3.0"
     },
     "conflict": {
         "drupal/drupal": "*"