* 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()'
* Adding variable to fade out ambiguity
* More readability on merge sorting algorithm
* Updating merge_sort_fastest description and explaining why
* Adding tests file with imports
* Standardazing filenames and function names
* Adding test cases and test functions
* Adding test loop
* Putting 'user oriented code' inside main condition for having valid imports
* Fixing condition
* Updating tests: adding cases and todo list
* Refactoring first euler problem's first solution
