remove dependencies

composer.json

@@ -23,9 +23,7 @@
   ],
   "minimum-stability": "stable",
   "require": {
-    "php-64bit": "^5.4 || ^7.0",
-    "ext-mbstring": "*",
-    "nelexa/buffer": "^1.1"
+    "php-64bit": "^5.4 || ^7.0"
   },
   "autoload": {
     "psr-4": {