Fixed tmux mouse config for version 2.1

tmux 2.1 broke the default mouse scrolling functionality. This mostly
fixes it. Also adds fast scrolling (half-page) with CTRL+wheel.

See tmux/tmux#145.

tmux.conf

@@ -70,7 +70,9 @@ setw -g window-status-current-fg brightgreen
 setw -g window-status-current-bg blue
 
 # Mouse support.
-setw -g mode-mouse on
-set -g mouse-resize-pane on
-set -g mouse-select-pane on
-set -g mouse-select-window on
+setw -g mouse on
+bind -n WheelUpPane if-shell -Ft = "#{mouse_any_flag}" "send-keys -M" "if -Ft= '#{pane_in_mode}' 'send-keys -M' 'select-pane -t=; copy-mode -e; send-keys -M'"
+bind -n WheelDownPane select-pane -t= \; send-keys -M
+
+bind -t vi-copy WheelUpPane   halfpage-up
+bind -t vi-copy WheelDownPane halfpage-down