multiprocess

Hi.

I use sitecopy to update my webpages and find it real useful.

As my main site is around 19GB it takes a long time to make the md5's.
Sitecopy uses 100% cpu on one core in around 2.5 minutes. 

So I have a feature request, if it is possible to make without too much
effort. It would be good if it was possible to use multiple cores to
calculate the md5's. As my current cpu has 4 cores it would speed up the
process a lot. And as new cpus are getting more and more cores it would
in the long run be an even better improvement.

/Anders