examples/benchmark.php: use our custom autoloader and not composer's.
examples/benchmark.php: use our custom autoloader and not composer's.

The vendor/autoload.php file may not be present, since it requires the
library to have been installed with composer to exist. Our custom
"autoload.php" on the other hand is always present, so this commit
changes the benchmark example to refer to our custom autoloader
instead.

maxmind/MaxMind-DB-Reader-php,jbboehr/MaxMind-DB-Reader-php,maxmind/MaxMind-DB-Reader-php,jbboehr/MaxMind-DB-Reader-php,jbboehr/MaxMind-DB-Reader-php,maxmind/MaxMind-DB-Reader-php