Sparsity-pattern

* set random seed for reproducibility

* Test multiple python versions
* Installation problems: zip_true set to False because file import required

* License changed to Apache-2

* triu and tril sparsity pattern added
* scipy example for README

* code reorganized
* `utils.get_matrix_dims_circle` to find matrix dimension and offset hyperparameters for a given number of matrix elements.

* Initial Release
* few more unit tests added
* examples for all sparsity patterns
* examples for scipy, tensorflow, pytorch