Add ext-ast to dev

Author: TysonAndre

composer.json

@@ -3,11 +3,11 @@
     "description": "A php-parser to php-ast converter written in php",
     "require": {
         "php": ">=7.1",
-        "nikic/PHP-Parser": "3.0.5",
-        "ext-ast": "~0.1.4"
+        "nikic/PHP-Parser": "3.0.5"
     },
     "require-dev": {
-        "phpunit/phpunit": "~6.2"
+        "phpunit/phpunit": "~6.2",
+        "ext-ast": "~0.1.4"
     },
     "autoload": {
         "psr-4": {"ASTConverter\\": "src/ASTConverter"}