Lock composer deps so that pipelines work

Author: Galbar

composer.json

@@ -16,7 +16,8 @@
     "require-dev": {
         "phpunit/phpunit": "~4.0",
         "sami/sami": ">=3.3.0",
-        "satooshi/php-coveralls": ">=1.0.1"
+        "satooshi/php-coveralls": ">=1.0.1",
+        "blackfire/php-sdk": "~1.31.0"
     },
     "autoload": {
         "psr-4": {