Fixed bugs in transitionFinder.tunnelFromPhase().
Tunneling should now work even when there is a barrier at T=0.

The first bug was easy to fix: I was using a size-1 numpy array where
I should have been using a float. This caused hash errors.

The other bug was that the minimization routine to find the point of
highest tunneling rate (S/T) would get stuck in regions where tunneling
couldn't happen at all. I've added some extra logic to make sure that
the initial guess for the minimization is more reasonable.