Reset position when reaching end of file

If I finished watching a 100s video with "mplayer-resume" and wanted to watch it again, I would get started at 99s or so. This patch solves this problem, i.e. it gets me started at the beginning.

Tested on Arch Linux with the following packages:
- mplayer-vaapi 35107-8
- python 3.3.2-1

More details upon request.