update deps; add branch-alias for better dep resolution by composer

Author: ashnazg

composer.json

@@ -23,5 +23,10 @@
     "mockery/mockery":  "~1.0",
     "league/flysystem-memory": "~1.0",
     "phpunit/phpunit": "^6.5"
+  },
+  "extra": {
+    "branch-alias": {
+      "dev-master": "1.x-dev"
+    }
   }
 }