Parametric battery holder

Parametric battery holder inspired by accucaps:
http://www.thingiverse.com/thing:115711

Actually I first produced this, then found that enif already done that:
http://www.thingiverse.com/thing:137582

However, that was a fun time searching for workarounds for making arcs in OpenSCAD, that's why I upload it anyway. It's simple and straightforward.