* Added doctest and more explanation about Dijkstra execution.
* tests were not passing with python2 due to missing __init__.py file at number_theory folder
* Removed the dot at the beginning of the imported modules names because 'python3 -m doctest -v data_structures/hashing/*.py' and 'python3 -m doctest -v data_structures/stacks/*.py' were failing not finding hash_table.py and stack.py modules.
* Moved global code to main scope and added doctest for project euler problems 1 to 14.
* Added test case for negative input.
* Changed N variable to do not use end of line scape because in case there is a space after it the script will break making it much more error prone.
* Added problems description and doctests to the ones that were missing. Limited line length to 79 and executed python black over all scripts.
* Changed the way files are loaded to support pytest call.
* Added __init__.py to problems to make them modules and allow pytest execution.
* Added project_euler folder to test units execution
* Changed 'os.path.split(os.path.realpath(__file__))' to 'os.path.dirname()'
* Wrote most of an rbt, missing just removal
* Added some convenience methods.
* Added a color method
* Wrote code to delete, but has issues :(
* Fixed a bug in Red-Black trees
* Fixed bug in tree color validation and delete repairing
* Clean up == comparison to None
* Added print function into matrix_multiplication_addition.py and removed blank space in data_structures/binary tree directory
* Removed .vs/ folder per #893
* Rename matrix_multiplication_addition.py to matrix_operation.py
* organized graph algorithms
* all graph algorithms in Graphs/ folder
* all graph algorithms are in one folder
* Rename number theory/factorial_python.py to maths/factorial_python.py
* Change some Image File names & re-code the psnr algorithm (conserving both methods). Also Added new example.
* Selected psnr method and reformat some code from arithmetic_analysis
