Modified Class to allow DS18B20 reading with different resolutions

[pmulvey]

I added write_scratch and read_temp to class.
read_temp uses the bit resolution values of 9 - 12 and incorporates the correct delay for data acquisition.

How to use:

from machine import Pin
from onewire import DS18X20
from onewire import OneWire

ow = OneWire(Pin('P8'))
temp = DS18X20(ow)
while True:
    print(temp.read_temp(9))
    print(temp.read_temp(10))
    print(temp.read_temp(11))
    print(temp.read_temp(12))
    print("----------------")

Output:

23.5
23.25
23.125
22.9375
----------------

The temperature was dropping hence the last reading is lower.

onewire.py