Update composer.json

Author: monkenWu

composer.json

@@ -13,6 +13,7 @@
             "email": "610877102@mail.nknu.edu.tw"
         }
     ],
+    "minimum-stability": "stable",
     "require": {
         "php" : "^7.1"
     },
@@ -22,4 +23,4 @@
 			"monken\\": "src/"
 		}
 	}
-}
+}