Update composer.json to require PHP >= 5.4

for short [] array declaration syntax.

Author: Craig Manley

Diff for: composer.json

@@ -12,7 +12,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.3.0"
+		"php": ">=5.4.0"
 	},
 	"autoload": {
 		"psr-4": {