Require Psysh ourselves.

...so consumers of this project can't forget it.

Author: beporter

composer.json

@@ -22,7 +22,8 @@
   "require": {
     "php": ">=5.4",
     "cakephp/cakephp": "~3.0",
-    "composer/installers": "~1.0"
+    "composer/installers": "~1.0",
+    "psy/psysh": "@stable"
   },
   "require-dev": {
     "phpunit/phpunit": "~4.1",