Prusa i3 Add-On X Tensioner

___[2014-11-24] Improved supports, increased hole slop, added more standard options.___

There are a lot of X idlers with a tensioner mod for the Prusa i3. But why print an entirely new idler when all you really need is a tensioner that fits your existing one? This simple, concise add-on x-axis belt tensioner can be used with most existing Prusa i3 x idlers and requires very little material. If you have an unusual x-idler or another printer with a similar design, you can modify the included SC