Feature request: watch folder

[r1ch]

Mostly, firstly:

This is superb - thank you very much - it works beautifully (on a Raspberry Pi no less).

I'm using it to watch a folder populated by a motion triggered camera. Sadly I'm a node.js guy so my approach is batch up 50 pictures and send them to gpup (using caolan/async cargo); works like a dream, but if you happened to want a challenge a -w path to folder would be great.

Thanks again.