add dev branch alias

Author: jaapio

composer.json

@@ -17,5 +17,10 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^4.6"
+    },
+    "extra": {
+        "branch-alias": {
+          "dev-master": "1.0.x-dev"
+        }
     }
 }