18650 Fatshark case - remixed

A remix of the original to fit a different cell checker board: http://www.banggood.com/2S-3S-4S-5S-Lipo-Battery-Voltage-Display-Indicator-Board-Polymer-Power-Indicator-Panel-p-1095698.html

A few other modifications:
- made the top and bottom flat so they printed better (no bridging). They are also thinner, so the overall battery length is shorter.
- the bottom is joined to the body
- made the top part that inserts into the body a little thicker. I found this was fragile.
- slit added s