Printrbot Simple Metal Fan Upgrade V2

After releasing my initial upgrade, I came across several issues: the pressure of the shroud was too great for the wee little CPU fan, the large size of the shroud meant it was prone to damage, and the shroud also hit the Printrbot's base when it was homed. This updated version has fixed all of these issues, most notably with a smaller, but stronger fan. This new fan has a higher amount of torque, and can much better handle the pressure created.