Checking to make sure tmux is actually installed before running plugin.

If it is not found an error message is printed.

plugins/tmux/tmux.plugin.zsh

@@ -1,3 +1,6 @@
+# Only run if tmux is actually installed
+if which tmux &> /dev/null
+	then
 	# Configuration variables
 	#
 	# Automatically start tmux
@@ -80,3 +83,6 @@ then
 			zsh_tmux_plugin_run
 		fi
 	fi
+else
+	print "zsh tmux plugin: tmux not found. Please install tmux before using this plugin."
+fi