support for acurite5n1

as discussed in #42 here is a basic, working merge worthy PR for support of Acurite 5n1 sensor. 
I'll look at implementing some other refactorings in another PR.

output looks like:
```
Detected Acurite 5n1 sensor
wind speed: 5 kph, wind direction: 90.0°, rain gauge: 0.00 in.
Detected Acurite 5n1 sensor
wind speed: 6 kph, temp: 81.3° F, humidity: 76% RH
```