Update vi-mode bindings for tmux 2.4

tmux/tmux#592

Also explicitly name tmux 2.4 in the readme

README.md

@@ -1,5 +1,6 @@
 ## Dependencies
 
+- tmux 2.4
 - ZSH/oh-my-zshell
 - For Ruby: rbenv
 - For JS: yarn

tmux.conf

@@ -89,10 +89,13 @@ set-option -g allow-rename off
 
 # https://robots.thoughtbot.com/tmux-copy-paste-on-os-x-a-better-future
 # Setup 'v' to begin selection as in Vim
-bind-key -t vi-copy v begin-selection
-bind-key -t vi-copy y copy-pipe "reattach-to-user-namespace pbcopy"
+bind-key -Tcopy-mode-vi 'v' send -X begin-selection
+bind-key -Tcopy-mode-vi 'y' send -X copy-pipe "reattach-to-user-namespace pbcopy"
 
 # Update default binding of `Enter` to also use copy-pipe
+unbind -Tcopy-mode-vi Enter
+bind-key -Tcopy-mode-vi Enter send -X copy-pipe "reattach-to-user-namespace pbcopy"
+
 unbind -t vi-copy Enter
 bind-key -t vi-copy Enter copy-pipe "reattach-to-user-namespace pbcopy"