Build and tests are fixed

I just tried to compile the library and run the tests, but in order to do so, I had to make the following changes (how could you compile and run it without them?)
- **Makefile**: When building library, makefile doesn't complain about non-existing directories (*added `-f` option when removing folders*)
- **Tests**: .obj file paths are correct now (*I had to add `../` since the two were in separate directories*)