Updated minimum required PHP version too 5.6

Author: janw-me

composer.json

@@ -198,7 +198,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.4",
+		"php": ">=5.6",
 		"ext-json": "*",
 		"wp-cli/admin-command": "dev-master",
 		"wp-cli/automated-tests": "dev-master",
@@ -251,7 +251,7 @@
 	},
 	"config": {
 		"platform": {
-			"php": "5.4"
+			"php": "5.6"
 		},
 		"process-timeout": 7200,
 		"sort-packages": true