Look for Vim in tmux pane's tty process list via ps/grep (#117)

This turned out to be a very robust method of detecting Vim processes,
and allows to ignore stopped ones (via `Ctrl-Z`).

Fixes #96.
Closes #117.

README.md

@@ -53,14 +53,15 @@ Add the following to your `tmux.conf` file to configure the tmux side of
 this customization.
 
 ``` tmux
-# Smart pane switching with awareness of vim splits
+# Smart pane switching with awareness of Vim splits.
 # See: https://github.com/christoomey/vim-tmux-navigator
-is_vim='echo "#{pane_current_command}" | grep -iqE "(^|\/)g?(view|n?vim?x?)(diff)?$"'
-bind -n C-h if-shell "$is_vim" "send-keys C-h" "select-pane -L"
-bind -n C-j if-shell "$is_vim" "send-keys C-j" "select-pane -D"
-bind -n C-k if-shell "$is_vim" "send-keys C-k" "select-pane -U"
-bind -n C-l if-shell "$is_vim" "send-keys C-l" "select-pane -R"
-bind -n C-\ if-shell "$is_vim" "send-keys C-\\" "select-pane -l"
+is_vim="ps -o state= -o comm= -t '#{pane_tty}' \
+    | grep -iqE '^[^TXZ ]+ +(\\S+\\/)?g?(view|n?vim?x?)(diff)?$'"
+bind-key -n C-h if-shell "$is_vim" "send-keys C-h"  "select-pane -L"
+bind-key -n C-j if-shell "$is_vim" "send-keys C-j"  "select-pane -D"
+bind-key -n C-k if-shell "$is_vim" "send-keys C-k"  "select-pane -U"
+bind-key -n C-l if-shell "$is_vim" "send-keys C-l"  "select-pane -R"
+bind-key -n C-\ if-shell "$is_vim" "send-keys C-\\" "select-pane -l"
 ```
 
 Thanks to Christopher Sexton who provided the updated tmux configuration in