Monoprice MP Select Mini 3D Printer Spool Holder

Small changes to cantizzy's spool holder:
1. Made slightly wider to allow for 1kg spools from Monoprice to be used
2. Shortened a bit - I don't use any spools that needed this height ~2cm
3. Improved the tolerances where the sides attach so they'll attach more easily (still stay securely connected)
4. Added a clip that secures the base to the stock spool holder
5. Improved the tightness and fit of the base to the stock spool holder - it is now very snug

To assemble:
1. Slide the base on from the end - flat side toward the printer, it will be tight as passes the upturned end, but should slide on, slide it up the base a bit.
2. Slide the clip onto the end of the base. Pointed side should be on top.
3. Slide the base back under the clip until the point catches.
4. Slide on sides so they are angled away from printer.
5. Slide in axle (with spool) and turn to lock.