Add composer.json

This add php parallel lint test. Can be triggered using the entry
point:

 composer test

That ease Jenkins integration and let developers add more testing
utilities as needed.

Change-Id: I2bf0dbea9f559267001eb727c7ecfeb103717464

composer.json

@@ -0,0 +1,10 @@
+{
+	"require-dev": {
+		"jakub-onderka/php-parallel-lint": "0.9"
+	},
+	"scripts": {
+		"test": [
+			"parallel-lint . --exclude vendor"
+		]
+	}
+}