Uploading files

As I see file uploads are still not possible, even though the fix was suggested some 4 years ago.

Currently I needed to post files and I wasn't in the mood for rewriting stuff in my app, so this is what I came up with:

$hooks = new Requests_Hooks();
$hooks->register('curl.before_send', function ($ch) {
  if (function_exists('curl_file_create')) { // php 5.5+
    $cFile = curl_file_create($_FILES['uploadFile']['tmp_name'], '', $_FILES['uploadFile']['name']);
  } else { // 
    $cFile = '@' . realpath($_FILES['uploadFile']['tmp_name']);
  }
  $_POST['uploadFile'] = $cFile;
  
  curl_setopt($ch, CURLOPT_POSTFIELDS, $_POST);
});
$resp = Requests::post($url, $headers, [], $options);

Just sharing in case it helps someone.

Close when #313 is ready :)

The issue includes a PHP Requests_Hooks workaround using the curl.before_send hook and refers to #313. Start by reading #313 and the request-handling entry points it identifies. Done means file uploads are supported without requiring callers to modify the request through a custom hook.