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.
fix for failed download with no subtitles when requested

Cleanup, traverse the list of args backwards, match all possible languages, regex in global var
fix for failed download with no subtitles when requested

consistency
fix for failed download with no subtitles when requested

update
fix for failed download with no subtitles when requested

update
fix for failed download with no subtitles when requested

this should do it ...
Merge pull request #37 from przemyslawpluta/master

fix for failed download with no subtitles when requested