v0.3.1T Final v0.3 release

Update README.md

v0.3T - Ventmon Tester 0.3

This release contains the firmware as distribute in the most recent 10 VentMons. It also contains the PCB design files and 3D printable files for that hardware configuration. The "T" in the release name stands for "Tester". Although we hope the VentMon will someday be incorporated into a pandemic response ventilator, it is not yet ready to be a life-critical medical monitoring device.

v0.2 - final release before major reorg

This is the last version before a major merge to begin the v0.3 release, which reorganizes the code in preparation for a PCB-based hardware solution.