differences of transfer matrix method to SpecularReflectivityModel

[dkriegner]

The transfer matrix method implemented in DynamicalReflectivityModel yields identical results to SpecularReflectivityModel

see the examples/simpack_xrr_matrixmethod.py script and the plot it generates

The benchmarking shows:

%timeit Reflec_S, Trans_S = model_S.simulate(alpha)
10 loops, best of 3: 56.9 ms per loop

%timeit R_kin = xrr_model.simulate(alpha)
1000 loops, best of 3: 404 µs per loop

that SpecularReflectivity is clearly faster.

If the results are equal under all cases it should be clearly stated in the example script.
If there are differences under certain cases these should be shown in the example script.

[dkriegner]

@nlaanait: I would be interested to get your opinion on this issue

[dkriegner]

@nlaanait: bump