Limit relative humidity

[caternuson]

Using non-NIST traceable human breath.

BEFORE

Adafruit CircuitPython 4.0.0 on 2019-05-20; Adafruit Metro M4 Airlift Lite with samd51j19
>>> import board
>>> import adafruit_si7021
>>> sensor = adafruit_si7021.SI7021(board.I2C())
>>> sensor.relative_humidity
96.5658
>>> sensor.relative_humidity
100.785
>>> sensor.relative_humidity
101.349
>>> sensor.relative_humidity
102.547
>>> sensor.relative_humidity
103.608

AFTER

Adafruit CircuitPython 4.0.0 on 2019-05-20; Adafruit Metro M4 Airlift Lite with samd51j19
>>> import board
>>> import adafruit_si7021
>>> sensor = adafruit_si7021.SI7021(board.I2C())
>>> sensor.relative_humidity
98.1145
>>> sensor.relative_humidity
100.0
>>> sensor.relative_humidity
100.0
>>> sensor.relative_humidity
100.0

[ladyada]

lol