Issue #13: Fixes dark webcam images on Mac.

Referencing: http://answers.preyproject.com/topics/webcam-images-are-dark-fix-included

I was also experiencing dark pictures taken from my new MacBook Air to the point where they really didn't help much. I've tested this fix and pictures are much better.

The imagesnap binary has been updated to v0.2.5 to support the new -w (wait) parameter.