add swoole/ide-helper package for dev

Author: killtw

composer.json

@@ -35,7 +35,8 @@
     "php-coveralls/php-coveralls": "^2.1",
     "mockery/mockery": "~1.0",
     "codedungeon/phpunit-result-printer": "^0.14.0",
-    "php-mock/php-mock": "^2.0"
+    "php-mock/php-mock": "^2.0",
+    "swoole/ide-helper": "@dev"
   },
   "autoload": {
     "files": [