Extracted and interface from the Reddit class and added some more folders to the project

Hey,
I'm creating a pull request for every few commits so there won't be a lot of changes at once, let me know if there is another way that is more convenient for you.

- Added some folders and moved some stuff around (purely cosmetic)
- Extracted an interface from the Reddit class and changed everywhere that can use IReddit instead of Reddit (easier if we want to add unit tests).