Order book enhancement

I added two new options to the order_book command: funded and digits. If funded is set to true, orders will be displayed for as much as they are funded. Setting digits will control in how many decimal digits will be in the output. I added these features for my own use, but I figured others can use them as well. I also added a command demonstrating these in the README and added my contact in the contacts.

P.S. Up until a few hours ago, I knew absolutely no Ruby, so you may want to look over it and make sure that it is safe / follows Ruby conventions. Thanks!