v0.11, June 18, 2014 -- Initial release.op	
v0.12, June 26, 2014 -- Update with masking, completely black interrogation window is masked
v0.13, June 30, 2014 -- Dynamic masking is included, image and velocity set to zero, sig2noise to infinity
v0.17, July 1, 2014  -- Fixed the bug in lib.pyx of different casting of np.int32 on 64-bit machines
v0.18  Aug. 8, 2014 -- small updates to the tutorial-part1, MANIFEST.IN, readme and install files
...
v0.22.3 Sep. 22, 2020 -- @erfan-mtr added two-phase extension, see phase_separation.ipynb for the demo
v0.22.4 Nov, 2020 -- windef refactoring : no more process.pyx, everything in pyprocess.py, numpy vectorized correlation version from windef moved to pyprocess, get_field_shape has less arguments (it's a backward compatability problem, it breaks stuff), new tests, new documentation settings with Jupyter notebook and markdown inserts, tools.save requires also sig2noise column, as in windef, frame_interpolation is now deform_windows with optionaly kx,ky, 
v0.23.0 - refactored windef.py, with the main functions moved to pyprocess.py
v0.23.1 - fixed bugs in 0.23.0, new normalized_correlation, normalize_intensity, find_subpixel_position, new tests, new jupyter notebooks, see also 
            test_robustness
v0.23.2 - added mask_coordinats to preprocess, allows to use dynamic_masking to create
    image mask as well as a polygon that propagates into multi-process and validation
    created new Jupyter notebook to test von Karman vortex street case and compare with PIVLab
    breakes backward compatibility of windef with removing validation and filtering steps, to be compatible
    with the first_pass. Both first_pass and multi_pass now apply filtering externally
    
v0.23.6 - removed widim.pyx, no Cython modules anymore
v0.23.7 - @ErichZimmer provided rectangular windows and we moved the test cases to another repo openpiv-python-examples

