Update main readme

thoughts? I'm really slimming down the main file - it's so dense no one was reading it. I think we should rely on links for complex issues like passwordless sudo, passwordless ssh, etc. These things are tough to get right in a general sense anyway, and they prevent anyone from ever getting to the details of how TFB works from a high level - they are too busy focusing on the string of 100 commands in front of them. I'm not against big strings of commands, but they should either be external links or links to another, more detailed readme file