Correct a bug with ffmpeg where it will wait forever for the user to answer a question when trying to overwrite a file.

Fix #68

src/video/stream.ts

@@ -24,6 +24,7 @@ export default function(rtmpUrl: string, rtmpInputPath: string, swfUrl: string,
   else if (mode === 'HLS')
   {
       cmd = command('ffmpeg') + ' ' +
+          '-y ' +
           '-i "' + rtmpInputPath + '" ' +
           '-c copy -bsf:a aac_adtstoasc ' +
           '"' + filePath + '.mp4"';