Fix a bug and add a test.
Merge pull request #189 from gassmoeller/fix_adiabatic

Fix a bug and add a test. We had a bug in the initial condition 'adiabatic' that only got triggered if one used a model with the bottom boundary layer parameter set to some value and without adiabatic heating. The temperature difference between model and boundary temperature was calculated wrong in this case. This pull request should fix this bug and add a test for this case.