#189 Force refresh

[rargh]

My update_interval right now is needlessly fast for everything except for things I change myself, e.g. the screen brightness, volume, and mpd_track. I'd like to see these update whenever I change them, but I don't need everything to update constantly.

So what I'd suggest, is somehow have the ability to force a refresh; when I run a certain command, conky refreshes. This way I could have my MPD hotkeys also refresh conky, so I can instantly see which song comes up, but I can keep the update interval infrequent.