PocketBeagle Enclosure Remix

I really like tinkeringtech's enclosure for the pocketbeagle, and made a couple revisions to it:
- There's a cutout for the cpu in the bottom piece. For cooling, you get to see the sticker on top of the cpu, and keeps the board centered within the case.
- Two rails on the side of the bottom piece to keep the board level within the case.
- The top piece has been made taller, so the board is sandwiched in place inside the case.
- The openings on the top piece have been slightly widened on the outer edges to accommodate female headers on the pocketbeagle.
- I found the top piece to fit a little loosely inside the bottom piece, so I've added a couple bumps on the side of the top piece to fit a little tighter.

I used OpenSCAD to modify the original STLs, and I've included the scad files. The pictures that thingiverse generates from the scad files are inaccurate because it doesn't know how to process the import of the STLs, so you'll need to download the original stl's and the scad