[Plugin: FireStats Charts] Dashboard bug fix

The graph image stretches too wide on the dashboard.
Proposed solution: change the image code from
echo ‘<div style=”text-align: center;”><img src=”‘.$this->absUrl.’out/’.$graphKey.’.png” alt=”‘.__(‘FireStats Graph’).'” /></div>’;

to

echo ‘<div style=”text-align: center;”><img src=”‘.$this->absUrl.’out/’.$graphKey.’.png” alt=”‘.__(‘FireStats Graph’).'” style=”width: 100%;” /></div>’;