added docblock to testGetInvalidPlantByPlantType()
added docblock to testGetInvalidPlantByPlantType()

https://app.asana.com/0/201562232002815/205761505868163

rdicharry/growify-fork-20161209,rdicharry/growify-fork-20161209,DannyEaton/growify,rdicharry/growify-fork-20161209,DannyEaton/growify,DannyEaton/growify