Spark Core Case V1

Description

This is an updated version of my previous case. The v0 had several issues when 3D printed: * the pattern on the lid wasn't thick enough, which made filling impossible. I simplified the pattern with fewer cells, and made the lines thicker. * the hole for the Micro USB port was too low. I moved it a millimer higher, and made the hole larger for better tolerance. Here's a picture of the v0 printed: