Remove misleading message from MultiAreaModel Class
Change NotImplementedError to TypeError
Adapt test
Improve documentation in README

Make Python 3 dependency explicit

RE-integrated SLN-R-Fit into scripts, but remove SLN_logdensities.R and deactivate SLN Fit for now because of cell density data copyright issue

Remove dependency from h5py_wrapper completely: Store data in binary numpy data files, add test_analysis to test analysis class, fix many bugs in analysis and analysis_helpers