New edstomo module and io features added

We are pleased to release the 1.5.0 version of ncempy. Please see the major changes below

This version has one major addition from @ZGainsforth providing methods for reconstructing STEM-EDS tomography maps. This adds some extra dependencies and example data files. To install this feature you need use pip with the following command:
pip install “.[edstomo]”

io/dm.py and io/mrc.py now include a getMemmap() function for accessing large datasets on disk without loading the entire data set into memory. 4D-STEM data and large movie files from the CETA2 are two examples where this can be a very useful function. More memmap functions will be included in future releases as data sets get larger and larger.

emd.py can now write datasets with keyword arguments passed directly to h5py. This allows compression and other features to be used transparently. Also emd.py can now retrieve meta data from an emd group without loading the entire data set. Check out the get_emddims function. Thanks again, @ZGainsforth!

More attention to the algorithms and evaluation routines is planned for the next release as the io module seems to be stabilizing without the need for major fixes or features.

Any feedback is welcome. Please add issues to the github page if you find errors or want new features added.