Use /cygdrive when rsyncing on Windows

Hi there,

I was trying to use the plugin on windows and it worked great until rsync failed:

"The source and destination cannot be both remote"

I'm using cygwin rsync by putting C:\cygwin\bin on my PATH. Changing hostpath to use /cygdrive/c rather than C:/ made rsync work.

This pull request is hard coded to the C drive, which I imagine could be an issue. If so, I'm happy to reconsider, maybe use a regex to replace the initial drive letter.

Still, opening this in case it is interesting.