If anyone is reading the file they will know to install `python3-smbus`,
but if someone just do a quick `pip3 install bme680` then make sure to pull smbus from PyPI
Note: on subsequent gas measurements the last temperature instead of 25 degree C will be used.
Nearly irrelevant because this happens to return value of _calc_heater_resistance(200):
ambient_temperature = 30 -> int(84.9119287004)
ambient_temperature = 25 -> int(84.9119068473)
ambient_temperature = 20 -> int(84.9118849941)
ambient_temperature = 10 -> int(84.9118412877)
According to the datasheet the resolution delivered by the sensor is better
than 1 degree Celsius, 1 Pascal, 1 percent relative humidity etc. The user
should have the possibility to get floating point precision and figure out
what the measurement accuracy allows given their settings.
When running the `examples/read-all.py` script I was seeing a crash because
the value passed to `write_i2c_block_data` wasn't being converted to an int:
```
File "/home/pi/tmp/bme680/library/bme680/__init__.py", line 281, in _set_regs
self._i2c.write_i2c_block_data(self.i2c_addr, register, value)
TypeError: Third argument must be a list of at least one, but not more than 32 integers
```
This commit ensures `set_gas_heater_temperature` converts the temperature to an int
before it's passed to `self._set_regs`.
