Flexible Filament Upgrade

Made the walls a bit thicker as to eliminate the gaps on the sides, since this generic metal extruder is thinner than the one on the anycubic. Added a little tube to be glued to the pneumatic fitting to further reduce the gaps. Successfully printed a couple of small parts TPU after installing this upgrade to the extruder. Having a bit of trouble with longer prints, but I'm working on a fix.