update to Dingo 2.0.0-alpha1

Author: joselfonseca

composer.json

@@ -14,7 +14,7 @@
     ],
     "require": {
         "php": ">=7.0.0",
-        "dingo/api": "1.0.*@dev",
+        "dingo/api": "2.0.0-alpha1",
         "fideloper/proxy": "~3.3",
         "laravel/framework": "5.5.*",
         "laravel/passport": "^4.0",