tmux: reduce escape-time to 50ms

The default escape-time of 500ms made it very annoying to use vim inside
of tmux and 50ms seems to make vim responsive enough.

files/tmux.conf

@@ -29,6 +29,7 @@ unbind-key -T   copy-mode-vi MouseDragEnd1Pane # Stay in copy mode on drag end
 #
 # General
 #
+set -gs escape-time         50                  # avoid delays with ESC in vim
 set -g base-index           1                   # start window numbering from 1
 set -g default-terminal     "screen-256color"   # display 256 colors
 set -g history-limit        20000               # remember longer history