Simple Customizable Key Tag

**Update (28 Jan 2017)**
Changed the default font and added more options.

The original font was a mono-space font and looks kinda bad. I changed the default to a san-serif, and made it configurable.

I've also made the hole size configurable. If you find it unnecessarily large (...which it often is), you can now change it.

Pro-tip: Pause the print when it is halfway done and change to a different color filament. The contrast will make the text much more readable. You can easily pause th