Added small test program to see if we can use
the half-life formula to calculate a decay on the
arduino (and if the difference in the results
don't differ too much)
Added shofanduino2 program, much simpler since
some of the calculations are now done in the
sensor (filtering out noisy values).

Instead of 'avg' and 'max', we use envelope min
and max values that try to hug the humidity with
a slow moving function. The slow moving function
is based on the half-life equation, so the
parameters are more intuitive.
Don't switch the relays constantly, only when
changing states.

The previous code did this correctly, but due to
code simplifications this was removed as well. Not
a big problem, but it's nicer not to switch
constantly.
Code cleanup, added comments and removed cruft.
Updated year of copyright notice
Added documentation
Added information where I got my dependencies.