refnx/refnx: v0.1.5

0.1.5 fixed font size in pyqt GUI. script export from pyqt GUI can use either multiprocessing or MPI for parallelisation during MCMC sampling. speeded up reflectivity calculation, following on from changes made in 0.1.4 (if the imaginary part of a complex sqrt argument is very small, then the C++ calculation takes a lot longer). added a plot method to PlatypusNexus refactor util.PoolWrapper to util.MapWrapper allow the number of Stack repeats to be fittable. GUI option to only display those parameters (and datasets) that are going to be varied in a fit. update testimonials.bib "to code" button in Jupyter interactive modeller respects the transform popup