Battery Holder

This thing allows you to create a battery holder in pretty much any way you like. There are now too many types of batteries supported to make examples for all of them, but I've included a few random example STL files for common batteries in case you aren't comfortable with OpenSCAD.

**Supported Battery Types:**
- AA
- AAA (or N, or A23)
- C
- D
- 9V
- CR2
- Lithium-Ion Rechargeable Cells
* 5 digit codes except 75400
- Button Cells
* 3 digit codes starting with 4, 5, 6, 7, or 9
* 4 digit codes starting with 10, 11, 12, 16, 20, 23, 24, or 44
- Custom Round Cells
* Any diameter in 1/100ths of a millimeter.

This represents 8 standard battery types, 13 diameters of button cells (in any thickness), and 22 known standard sizes for lithium cells (but really almost any size they come up with). If for some reason you have a round battery that I don't explicitly support, there is now custom diameter support for anything you can measure and print. Hopefully t