Added headers methods, and RAW data var

[rodrigopolo]

Some times you need to know your rate limiting, and the only way to know it is by reading this HTTP headers:

x-rate-limit-limit
x-rate-limit-reset
x-rate-limit-remaining

So I added the method _setHeader to store the CURL received headers, and the getHeaderArray method to return an indexed array with the current HTTP headers after any request:

$my_headers = $twitter->getHeaderArray();

$current_time = time();
$time_to_next = $my_headers['x-rate-limit-reset'] - $current_time;
if($tw_headers['x-rate-limit-remaining']<1){
	echo "Sleeping for ".$time_to_next." seconds, or ".($time_to_next/60)." minutes .\n";
	sleep($time_to_next);
}

I also added the public instance of the RAW body, for development and debugging purposes.