Fix php-curl-class#563: Suggest updating composer

Author: zachborboa

TROUBLESHOOTING.md

@@ -49,3 +49,10 @@ $curl_error_message = curl_error($ch);
 $http_status_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
 $request_headers = curl_getinfo($ch, CURLINFO_HEADER_OUT);
 ```
+
+### Ensure you have the latest composer version installed
+
+```bash
+$ composer self-update
+$ composer --version
+```