Spool Holder for RailCore2

**Update:**

So I found a spool that was slightly bigger, and it dragged against the electrobox, so I've added a new model that's slightly elevated.

Look for an update to the filament guide thing, as well; it keeps popping out, so I'm going to make it taller and tighter.

**/Update**

If you're clumsy like me, and keep knocking the spools off the skate-bearing spool carrier we recommend with the RailCore, this might be a quick-n-dirty solution. I'm using it now and it seems to work fine. I'm using a bit of 6mm drill rod, but pencils work, too. These just slide over the extrusion+side of the Railcore2, and you throw a spool on it. They're a little longer than might seem necessary because they have to hold the spool above the electrobox.

The filament guide holder is designed so that you can remove and replace the filament guide from the holder without pulling the filament out of the hot end. Basically a 2mm slot for the filament, into a 4.25mm hole for the PTFE guide tube.