Do studies about the different minimization methods

[maxnoe]

we should do studies about the performance of the different minimization methods

[maxnoe]

Simple Gaussian fit to 1e6 Values: Powell 0.3 seconds BFGS 1.2 seconds

[ibab]

Would be nice to try out ceres as well. There are Python bindings via Cython here: https://github.com/rll/cyres, but they don't seem to contain the interface for minimizing general functions. It shouldn't be too difficult to add, though.