Refactored the examples slightly

Shows bad gateway error even if the ProxyHandler fails to load.
Uses the same method for all examples that looks like this:
```php
// Check for a success
if ($proxy->execute()) {
    //print_r($proxy->getCurlInfo()); // Uncomment to see request info
} else {
    echo $proxy->getCurlError();
}

$proxy->close()
```