fix for failed download with no subtitles

At the moment if video doesn't have subtitles `youtube-dl` fails with ... 

```js
events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: : video doesn't have subtitles

    at /test/youtube-dl/lib/youtube-dl.js:122:23
    at ChildProcess.exithandler (child_process.js:645:7)
    at ChildProcess.emit (events.js:98:17)
    at maybeClose (child_process.js:755:16)
    at Process.ChildProcess._handle.onexit (child_process.js:822:5)
```

... this fix catches and removes possible options passed by the user and tries once to download video only without the subtitles.

lib/youtube-dl.js

@@ -71,6 +71,7 @@ var ytdl = module.exports = function(url, args, options) {
  * @param {Function(!Error, String)} callback
  */
 function call(video, args1, args2, options, callback) {
+
  var args = args1.concat(util.parseOpts(args2));
 
  // Parse url.
@@ -98,9 +99,28 @@ function call(video, args1, args2, options, callback) {
 
  // Call youtube-dl.
  execFile(opt[0], opt[1], options, function(err, stdout, stderr) {
+
  if (err) return callback(err);
- if (stderr) return callback(new Error(stderr.slice(7)));
 
+ if (stderr) {
+
+ // Try once to download video if no subtitles available
+ if (stderr.indexOf('WARNING: video doesn\'t have subtitles') !== -1 && !options.nocc) {
+ var cleanupOpt = opt[1];
+
+ ['--write-sub', '--srt-lang=en', '--all-subs'].map(function map(item) {
+ var target = cleanupOpt.indexOf(item);
+ if (target > -1) { cleanupOpt.splice(target, 1); }
+ });
+
+ options.nocc = true;
+
+ return call(video, args1, cleanupOpt, options, callback);
+
+ }
+
+ return callback(new Error(stderr.slice(7)));
+ }
  var data = stdout.trim().split(/\r?\n/);
  callback(null, data);
  });
@@ -163,7 +183,7 @@ ytdl.getInfo = function(url, args, options, callback) {
 
  var playlist = [];
  var track = [];
- 
+
  data.forEach(function(row) {
  track.push(row);