src/Skeetr/Client/HTTP/Response.php
public function addHeader($header, $append = false)
    {
        if ( !$headers = Header::parse($header) ) return false;
        return $this->addHeaders($headers, $append);
    }
public function addHeader($header, $append = false)
    {
        if ( !$headers = Header::parse($header) ) return false;
        return $this->addHeaders($headers, $append);
    }
Add headers. If append is true, headers with the same name will be separated,
else overwritten.

@param string $header just a string with the header
@param array  $append if true, and a header of the same type allready exists will
append, if false will be replaced.
@return boolean Returns TRUE on success or FALSE on failure.