make it more obvious that i should try --skip 10

[jpritikin]

I kept getting blank images, but guvcview worked fine. I couldn't figure it out until I read somewhere in the issues about --skip 10. That solved it, but I wasted 2-3 hours trying to figure out why I wasn't getting images. You really ought to suggest --skip 10 near the beginning of the description instead of burried down in the list of options.