When using pyinstaller

1) setup a new conda environment, with just python=3.7
2) activate the environment
3) pip install pyqt6 numpy scipy cython matplotlib pandas xlrd h5py (numpy1.16 doesn't play well with pyinstaller)
4) pip install refnx pyinstaller
5) Change the version number in the motofit.spec file
6) pyinstaller slim.spec
