Do not make the /tmp/sketches directory world-writable or world-readable

In practice, a umask also applies to these permissions, so it would not
be world-writable anyway. Better to enforce this, and remove the
world-readability at the same time.

Author: matthijskooijman

main.go

@@ -187,7 +187,7 @@ func (p program) run() {
 		}
 	}
 
-	os.Mkdir("/tmp/sketches", 0777)
+	os.Mkdir("/tmp/sketches", 0700)
 
 	go addWatcherForManuallyAddedSketches("/tmp/sketches", sketchFolder, status)