Use latest Robo

Author: tauno

composer.json

@@ -66,7 +66,7 @@
  "mikey179/vfsStream": "~1.2",
  "phpunit/phpunit": "~4.8",
  "symfony/css-selector": "~2.8",
- "consolidation/robo": "~1"
+ "consolidation/robo": "dev-master"
  },
  "conflict": {
  "drupal/drupal": "*"