bump min php version in composer.json to 5.4

composer.json

@@ -6,7 +6,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.3.0",
+		"php": ">=5.4.0",
 		"pear-pear.horde.org/Horde_Date": "^2.0.0@stable",
 		"pear-pear.horde.org/Horde_Exception": "^2.0.0@stable",
 		"pear-pear.horde.org/Horde_Imap_Client": "^2.28.0@stable",