Add 'setprops' method to modify the settings for the specified
'hash', as described here:
http://www.utorrent.com/community/developers/webapi#devs8

Enables programmatic control of 'trackers' property.

Tested on uTorrent v1.8.4 on Mac OS X v10.8.5.
Merge pull request #2 from jso/master

Added 'setprops' method