Changes to support custom commands sent to each window

I love this tool and use it often. Recently I used it to connect to a server and wanted windows open for the access and errors logs of Apache and my app's system and error logs and a postgres window, etc. I got tired to doing that manually. After I did this I noticed the -X argument and that could probably be made to work, but this seems cleaner and a bit easier to use. 

Great project! Thanks for doing this.

Bill