Remove JSON polyfill

No longer supporting PHP 5.1.
Fixes #394

qa-include/qa-base.php

@@ -193,23 +193,6 @@
 
 		// Polyfills
 
-		// JSON compatibility layer for PHP 5.1
-		if (!function_exists('json_encode') && !function_exists('json_decode')) {
-			require_once QA_INCLUDE_DIR.'vendor/JSON.php';
-
-			function json_encode($json)
-			{
-				$service = new Services_JSON();
-				return $service->encode($json);
-			}
-
-			function json_decode($json, $assoc = false)
-			{
-				$service = new Services_JSON($assoc ? SERVICES_JSON_LOOSE_TYPE : 0);
-				return $service->decode($json);
-			}
-		}
-
 		// password_hash compatibility for 5.3-5.4
 		define('QA_PASSWORD_HASH', !qa_php_version_below('5.3.7'));
 		if (QA_PASSWORD_HASH) {