SmartThings Multipurpose Sensor (2015 & 2016) case with AAA batteries

After designing [thing:3212345](http://www.thingiverse.com/thing:3212345) and successfully having all my SmartThings motion sensors operating with AAA batteries, it only made sense to do the same with the SmartThings multipurpose sensors, of which I have a larger number. Although these sensors have a significantly better battery life than the movement detection counterparts, it still sucks to have to buy CR2450 cells and replace them every 6-8 months (in my experience, at least).

So, this is