Fix set_baseline method in class SGP30

[phooey]

As explained in this comment the set_baseline method of the SGP30 class has the wrong parameter order, and is also making an incorrect call to self.command.

In this pull request these issues are fixed and the set_baseline method can now be used to correctly set a new baseline.

With the following example it now works as expected with this change:

from sgp30 import SGP30
sgp30 = SGP30()

result = sgp30.get_baseline()
print("{:02x} {:02x}".format(result.equivalent_co2, result.total_voc))
sgp30.set_baseline(result.equivalent_co2, result.total_voc)
result = sgp30.get_baseline()
print("{:02x} {:02x}".format(result.equivalent_co2, result.total_voc))

=>

90d7 936b
90d7 936b

[Gadgetoid]

Thanks for doing the legwork here and PR'ing a fix, much appreciated!