Revert "use send-keys -R to clear terminal and remove the sleep call", fixes #538

Instead, increase the sleep delay

.tmux.conf

@@ -48,7 +48,7 @@ set -g display-time 1000      # slightly longer status messages display time
 set -g status-interval 10     # redraw status line every 10 seconds
 
 # clear both screen and history
-bind -n C-l send-keys -R \; clear-history
+bind -n C-l send-keys C-l \; run 'sleep 0.2' \; clear-history
 
 # activity
 set -g monitor-activity on