Successfully refactored code.

Changed made:

1. Data now in the form of list of Github ids instead of urls
2. Removed `get_username()` as it's unnecessary with changes in data structure
3. Added `syspath` parameter to functions to allow users to enter their own paths
4. Only tries to remove existing repos if there are existing repos (previous version raised `OSError: No such file or directory: '../repos'`)
5. Removed global variables and inserted them to top level `__main__` script to remove conflict of responsibility

Future to-do added to issues.